Methods and systems for controlling air flow paths in an engine

ABSTRACT

Methods and systems are provided for controlling a temperature of gases within a heat exchanger, a ratio of gases output by the heat exchanger, and selectively charging/discharging gases from the heat exchanger to one or both of an intake system or an exhaust system. In one example, a method may include controlling operation of an energy recovery device coupled to the heat exchanger in response to engine operating conditions, and increasing or decreasing flow of exhaust gas and/or compressed intake air into the heat exchanger in response to energy recovery device output.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 15/162,443, entitled “METHODS AND SYSTEMS FOR CONTROLLING AIRFLOW PATHS IN AN ENGINE,” filed on May 23, 2016. The entire contents ofthe above-referenced application are hereby incorporated by reference inits entirety for all purposes.

FIELD

The present description relates generally to methods and systems forcontrolling air flow paths of an internal combustion engine.

BACKGROUND/SUMMARY

Engine systems may utilize recirculation of exhaust gas from an engineexhaust system to an engine intake system, a process referred to asexhaust gas recirculation (EGR), to reduce regulated noxious emissions.Turbocharged engines may include a low-pressure EGR (LP EGR) system, ahigh-pressure EGR (HP EGR) system, or both. The LP EGR system divertsexhaust gases after the gases pass through the turbine of theturbocharger and injects the gases before the compressor, while the HPEGR system diverts exhaust gases before the turbine and injects thegases after the intake throttle. An EGR valve may be controlled ineither example to achieve a desired intake air dilution, the desiredintake air dilution based on engine operating conditions to maintaindesirable combustion stability of the engine while providing emissionsand fuel economy benefits.

An engine system may also utilize another separate approach to reducenoxious emissions that includes increasing exhaust gas temperatures byoperating the engine rich (e.g., increasing the ratio of fuel to airdelivered to cylinders of the engine) to generate high levels ofengine-out carbon monoxide (CO), hydrogen (H2), and hydrocarbons and atthe same time pumping air (herein referred to as secondary air injectionor SAI) into the exhaust manifold upstream of an emissions controldevice (such as an exhaust catalyst). The air pumped into the exhaustmanifold may react with the exhaust gases generating an exothermicreaction. As a result, rapid heating of the emissions control device maybe achieved and performance of the emissions control device increases,resulting in decreased noxious emissions.

However, the inventors herein have recognized issues with the aboveapproaches. An engine system including only a LP EGR system has a longtransport delay, as the exhaust gases travel through the turbochargercompressor, high pressure air induction plumbing, charge air cooler, andintake manifold before reaching the combustion chamber. As a result, itmay be difficult to provide the desired amount of EGR to the cylinders,particularly during transient conditions. This is due to the fact that,by the time the EGR reaches the cylinder, the engine speed/load statemay have changed and another EGR rate may be desired. An engine systemincluding only a HP EGR system has a reduced EGR delivery time, but thepercentage of EGR gases compared to intake gases may be limited and theability to provide sustained EGR delivery may be compromised by lowexhaust pressures. An engine system including a both a LP EGR system anda HP EGR system may experience energy losses due to increased cooling ofhot exhaust gases and an increased complexity of valve arrangement.Additionally, the ability to supply secondary air injection to theexhaust system may be controlled by an additional system separate fromthe LP and EGR systems, further increasing the complexity of the enginesystem arrangement. Further still, EGR gases are often cooled via an EGRcooler in order to reduce a risk of engine and/or compressor degradationdue to injection of hot EGR gases into the intake system. As a result,thermal energy of the hot EGR gases is wasted (e.g., the thermal energyis absorbed by coolant circulating through the EGR cooler) and theengine system may experience increased energy losses due to increasedengine load (e.g., increased fan speeds, increased coolant circulationand pump speeds, etc.) in order to cool the EGR gases via the EGRcooler.

In one example, the issues described above may be addressed by a methodfor flowing intake air through a heat exchanger and selectively to eachof an intake system and an exhaust system; flowing exhaust gas throughan energy recovery device coupled with the heat exchanger, through theheat exchanger, and selectively to each of the intake and exhaustsystem; and adjusting the flow of intake air and exhaust gas through theheat exchanger in response to an output of the energy recovery device.In one example of the heat exchanger, exhaust gases may selectively flowfrom both upstream and downstream of an emissions control device intothe heat exchanger and through the energy recovery device. Additionally,compressed intake air may selectively flow from downstream of acompressor and into the heat exchanger. The energy recovery device mayreceive thermal energy from the hot exhaust gases entering the heatexchanger and convert the thermal energy into electrical energy. Theexhaust gases may then travel through the remainder of the heatexchanger where a portion of the thermal energy remaining in the exhaustgases may transfer to fresh air within the heat exchanger, resulting inan increased temperature of the fresh air. The fresh air may then beprovided to the exhaust system in the form of secondary air injection,with the increased temperature of the fresh air enabling a moreefficient exothermal reaction between the fresh air and the engineexhaust gases, or returned to the intake system upstream of thecompressor to decrease compressor surge. The exhaust gases exiting theheat exchanger may be provided to the intake system in the form of LPEGR or HP EGR, with the decreased temperature of the exhaust gasesenabling a more efficient compression for increased compressor and/orengine performance. In this way, the output of the heat exchanger may becontrolled to supply low pressure LP EGR, HP EGR, secondary airinjection, air for compressor surge control, and exhaust energyrecovery. By controlling the temperature of the gases within the heatexchanger and the ratio of the gases output by the heat exchanger, theheat exchanger can be utilized with a wide variety of engine operatingconditions to increase engine performance and lower emissions.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first schematic of a system for an engine including aheat exchanger positioned between an intake system and an exhaust systemof the engine.

FIG. 2 shows a first embodiment of a heat exchanger including gas andcoolant passages internal to the heat exchanger and inlet and outletports coupled to the internal gas and coolant passages.

FIGS. 3A-3B illustrate an example method for adjusting a flow of coolantto a heat exchanger based on engine operating conditions.

FIG. 4 illustrates an example method for discharging pressurized airfrom a heat exchanger as secondary air injection into either an exhaustmanifold or a turbine bypass passage around a turbine based on engineoperating conditions.

FIG. 5 shows graphs illustrating example charging and dischargingoperations from a heat exchanger based on engine operating conditions.

FIG. 6 shows a second schematic of a system for an engine including aheat exchanger positioned between an intake system and an exhaust systemof the engine and an energy recovery device coupled to the heatexchanger.

FIG. 7 shows a second embodiment of a heat exchanger including gaspassages internal to the heat exchanger, gas inlet and outlet portscoupled to the internal gas passages, and an energy recovery devicecoupled to the heat exchanger.

FIG. 8 shows a third schematic of a system for an engine including aheat exchanger positioned between an intake system and an exhaust systemof the engine, an energy recovery device coupled to the heat exchanger,and coolant circulating through the heat exchanger.

FIG. 9 shows a third embodiment of a heat exchanger including gas andcoolant passages internal to the heat exchanger, inlet and outlet portscoupled to the internal gas and coolant passages, and an energy recoverydevice coupled to the heat exchanger.

FIG. 10 shows a method of increasing or decreasing energy recovery froman energy recovery device of a heat exchanger in response to engineoperating conditions.

FIG. 11 shows a method of adjusting intake, exhaust, and/or coolant flowto a heat exchanger in response to energy recovery device operatingconditions.

FIG. 12 shows graphs illustrating example energy recovery deviceoperation of a heat exchanger based on engine operating conditions.

DETAILED DESCRIPTION

The following description relates to systems and methods foraccumulating and/or distributing exhaust gases and intake air throughouta boosted engine system, such as the engine system shown by FIG. 1,wherein the engine system includes a heat exchanger (which may herein bereferred to as a mixing tank, flow mixing tank, or gas mixing tankreservoir). By accumulating, mixing, and/or flowing exhaust gases andintake air within the heat exchanger, such as the heat exchanger shownby FIG. 2, gases may be discharged into an intake system and/or anexhaust system to provide low-pressure exhaust-gas recirculation,high-pressure exhaust-gas recirculation, secondary air injection, and/orcompressor surge reduction. An engine controller may be configured toperform a control routine, such as the example method of FIGS. 3A-3B, tocharge the heat exchanger with one or more of combusted exhaust gas fromthe exhaust system or fresh intake air from the intake system (whencharging opportunities are available), and/or to discharge thepressurized charge from the mixing tank into the intake system and/orthe exhaust system based on engine operating conditions, as well as thecomposition of charge available in the mixing tank. Further, the flow ofcoolant through the heat exchanger may be controlled in order to deliverair from the heat exchanger to the intake and/or exhaust system at adesired temperature for the air injection application (e.g., HP EGR, LPEGR, or secondary air injection). The controller may also be configuredto perform a control routine, such as the example method of FIG. 4, todetermine whether to adjust a discharge of gases from the heat exchangerto the exhaust manifold and/or the turbine bypass passage when secondaryair injection and/or an increase in turbine rotational speed isadvantageous. Example charging and discharging operations are shown inFIG. 5.

In another embodiment, an engine system, such as the engine system shownby FIG. 6, may include an energy recovery device coupled to a heatexchanger. Hot exhaust gases from an exhaust system may flow into theheat exchanger and through the energy recovery device, where a portionof the thermal energy of the exhaust gases is converted into electricalenergy by the energy recovery device. The exhaust gases may then providethermal energy to intake gases flowing through the heat exchanger via aplurality of passages internal to the heat exchanger, as shown by FIG.7. In yet another embodiment, an engine system, such as the enginesystem shown by FIG. 8, may include a heat exchanger utilizing an energyrecovery device and a radiator circulating coolant between the heatexchanger and the radiator. The coolant may circulate through a volume(e.g., a series of passages) internal to the heat exchanger and mayexchange thermal energy with the intake gases and the exhaust gasesflowing through the heat exchanger (e.g., via separate flow passageswithin the heat exchanger), as shown by FIG. 9. For example, coolantpassages may be arranged proximate to the gas passages to permit heat totransfer from the gases into the coolant. In one example, the heatexchanger may include separate gas passages for the coolant flow,exhaust flow, and intake air flow such that the coolant, exhaust gases,and intake air do not mix with each other within the heat exchanger. Theoperation of the energy recovery device within the heat exchanger may becontrolled in response to engine operating conditions, as shown by FIG.10. In one example, engine operating conditions that may determine theoutput of the energy recovery device include exhaust temperature, engineload, particulate filter regeneration activation, etc. In response tooperation of the energy recovery device, flow of exhaust gases, intakesgases, and coolant to the heat exchanger may be adjusted, as shown byFIG. 11. Example operation of the energy recovery device, includingoutput of the energy recovery device in response to engine operatingconditions, is shown by FIG. 12.

By discharging gases from the heat exchanger into the exhaust system,turbine spin-up may be expedited and/or operating temperatures for oneor more emission control devices may be quickly reached. By utilizingthe output of the heat exchanger to enable high-pressure EGR to beprovided during high engine torque demand, low-pressure EGR to beprovided during low-to-moderate engine torque demand, and compressorsurge control to be provided when adjusting from high engine torquedemand to low engine torque demand, engine performance may be increased.Further, by adjusting the flow of coolant through the heat exchangerbased on a temperature of the coolant and desired air injectionapplication, a temperature of the air entering the intake or exhaustsystem from the heat exchanger may be controlled to a desiredtemperature. This may result in an increase in engine efficiency,decrease in engine emissions, and a decrease in compressor degradation.Additionally, by utilizing hot exhaust gases to convert thermal energyinto electrical energy via the energy recovery device, and to heat theintake air within the heat exchanger, energy may be more efficientlytransferred between mediums without using additional devices and/orenergy storage means. For example, various electrical loads of theengine may be supported using energy recovered by the energy recoverydevice from exhaust gases, thereby reducing a power usage of the engineand/or reducing additional batteries or electrical storage means.Further, in one example, by transferring heat between exhaust gas andintake air within the heat exchanger, additional cooling from a coolingsystem (e.g., coolant from a radiator) may be reduced or altogetheromitted. This may allow the engine to operate more efficiently andreduce power usage.

FIG. 1 schematically shows aspects of an example engine system 166including an engine 168. In the depicted embodiment, engine 168 includesan intake system 170 and an exhaust system 172. The engine 168 alsoincludes a turbocharger 174 with a compressor 184 arranged within theintake system 170 and a turbine 186 arranged within the exhaust system172. The compressor 184 is coupled to the turbine 186 by a shaft 171 anddriven by the rotational motion of the turbine 186. Specifically, freshair is introduced along intake passage 181 into engine 168 via aircleaner 183 and flows to compressor 184. The compressor may be anysuitable intake-air compressor, such as a motor-driven or driveshaftdriven supercharger compressor. In engine system 166, however, thecompressor is a turbocharger compressor mechanically coupled to turbine186 via shaft 171, and the turbine 186 is driven to rotate by expandingengine exhaust. In one embodiment, the compressor and turbine may becoupled within a twin scroll turbocharger. In another embodiment, theturbocharger may be a variable geometry turbocharger (VGT), whereturbine geometry is actively varied as a function of engine speed.

As shown in FIG. 1, compressor 184 is coupled, through charge-air cooler185 to throttle valve 187. Throttle valve 187 is coupled to engineintake manifold 176. From the compressor, the compressed air chargeflows through the charge-air cooler 185 and the throttle valve 187 tothe intake manifold 176. The charge-air cooler 185 may be an air-to-airor air-to-water heat exchanger, for example. In the embodiment shown inFIG. 1, the pressure of the air charge within the intake manifold 176 issensed by manifold air pressure (MAP) sensor 175. A compressor by-passvalve (not shown) may be coupled in series between the inlet and theoutlet of compressor 184. The compressor by-pass valve may be a normallyclosed valve configured to open under selected operating conditions torelieve excess boost pressure. For example, the compressor by-pass valvemay be opened during conditions of decreasing engine speed to avertcompressor surge.

Intake manifold 176 is coupled to a series of combustion chambers 180through a series of intake valves (not shown). The combustion chambersare further coupled to exhaust manifold 178 via a series of exhaustvalves (not shown). The combustion chambers 180 are capped by cylinderhead 182 and coupled to fuel injectors 179. In the depicted embodiment,a single exhaust manifold 178 is shown. However, in other embodiments,the exhaust manifold may include a plurality of exhaust manifoldsections. Configurations having a plurality of exhaust manifold sectionsmay enable effluent from different combustion chambers to be directed todifferent locations in the engine system. In the embodiment shown inFIG. 1, the pressure of the exhaust gases within the exhaust manifold178 is sensed by manifold air pressure (MAP) sensor 177.

In one embodiment, each of the exhaust and intake valves may beelectronically actuated or controlled. In another embodiment, each ofthe exhaust and intake valves may be cam actuated or controlled. Whetherelectronically actuated or cam actuated, the timing of exhaust andintake valve opening and closure may be adjusted as desired forcombustion and emissions-control performance.

Engine 168 may be controlled at least partially by a control system 167including controller 169 and by input from a vehicle operator via aninput device (not shown). Control system 167 is configured to receiveinformation from a plurality of sensors 165 (various examples of whichare described herein) and sending control signals to a plurality ofactuators 163. As one example, sensors 165 may include temperaturesensor 158 coupled to coolant inlet passage 160, temperature sensor 139coupled to flow mixing tank (also referred to herein as a heatexchanger) 100, temperature sensor 189 coupled to first emission controldevice 188, temperature sensor 191 coupled to exhaust conduit 193,temperature sensor 195 coupled to second emission control device 190,manifold air pressure sensor 175 coupled to intake manifold 176,manifold air pressure sensor 177 coupled to exhaust manifold 178, andpressure sensor 159 coupled to flow mixing tank 100. Various exhaust gassensors may also be included in exhaust system 172, within and/ordownstream of exhaust manifold 178, such as particulate matter (PM)sensors, temperature sensors, pressure sensors, NOx sensors, oxygensensors, ammonia sensors, hydrocarbon sensors, etc. Other sensors suchas additional pressure, temperature, air/fuel ratio and compositionsensors may be coupled to various locations in the engine system 166. Asanother example, actuators 163 may include fuel injector 179, valve 150coupled to surge control passage 152, valve 146 coupled to low-pressureexhaust gas recirculation passage 148, valve 138 coupled tohigh-pressure exhaust gas recirculation passage 140, valve 110 coupledto boost air passage 108, valve 118 coupled to exhaust inlet passage116, waste gate 133 coupled to turbine bypass passage 135, valve 162coupled to coolant inlet passage 160, and intake throttle 187. Actuators163 may also include three-way valve 130 coupled to second externalsplit passage 129, first secondary air injection passage 132, and secondsecondary air injection passage 131. Other actuators, such as a varietyof additional valves and throttles, may be coupled to various locationsin engine system 166. Controller 169 may receive input data from thevarious sensors, process the input data, and trigger the actuators inresponse to the processed input data based on instruction or codeprogrammed therein corresponding to one or more routines.

Controller 169 may be a microcomputer, and may include a microprocessorunit, input/output ports, an electronic storage medium for executableprograms and calibration values such as a read only memory chip, randomaccess memory, keep alive memory, and/or a data bus. Controller 169 mayreceive various signals from sensors coupled to engine 168, in additionto those signals previously discussed, including measurement of inductedmass air flow (MAF) from a mass air flow sensor; engine coolanttemperature (ECT) from a temperature sensor coupled to a cooling sleeve;a profile ignition pickup signal (PIP) from a Hall effect sensor (orother type) coupled to a crankshaft; throttle position (TP) from athrottle position sensor; absolute manifold pressure signal (MAP) fromone or more intake and exhaust manifold sensors, cylinder air/fuel ratiofrom an exhaust gas oxygen sensor, and abnormal combustion from a knocksensor and a crankshaft acceleration sensor. Engine speed signal, RPM,may be generated by controller 169 from signal PIP. Manifold pressuresignal MAP from a manifold pressure sensor may be used to provide anindication of vacuum, or pressure, in the intake manifold.

Storage medium read-only memory can be programmed with computer readabledata representing instructions executable by a processor for performingthe methods described below as well as other variants that areanticipated but not specifically listed. Example routines are shown withreference to FIGS. 3A-6.

FIG. 1 shows electronic control system 167, which may be any electroniccontrol system of the vehicle in which engine system 166 is installed.In embodiments where at least one intake or exhaust valve is configuredto open and close according to an adjustable timing, the adjustabletiming may be controlled via the electronic control system to regulatean amount of exhaust present in a combustion chamber during ignition.The electronic control system may also be configured to command theopening, closure and/or adjustment of various other electronicallyactuated valves in the engine system-throttle valves, compressor by-passvalves, waste gates, EGR valves and shut-off valves, secondary airvalves, various reservoir intake and exhaust valves, for example-toenact any of the control functions described herein. Further, to assessoperating conditions in connection with the control functions of theengine system, the electronic control system may be operatively coupledto a plurality of sensors arranged throughout the engine system-flowsensors, temperature sensors, pedal-position sensors, pressure sensors,etc.

Combustion chambers 180 may be supplied one or more fuels, such asgasoline, alcohol fuel blends, diesel, biodiesel, compressed naturalgas, etc. Fuel may be supplied to the combustion chambers via directinjection, port injection, throttle valve-body injection, or anycombination thereof. In the combustion chambers, combustion may beinitiated via spark ignition and/or compression ignition.

As shown in FIG. 1, exhaust from the one or more exhaust manifoldsections is directed to turbine 186 to drive the turbine 186. Theexhaust passes through a first emission control device 188 while flowingtowards turbine 186. When reduced turbine torque is desired, someexhaust may be directed instead through a waste gate 133 into a turbinebypass passage 135, by-passing the turbine. The combined flow from theturbine 186 and the waste gate 133 then flows through second emissioncontrol device 190. In the embodiment of the engine system 166 shown byFIG. 1, the second emission control device 190 has a larger exhaustprocessing capability than the first emission control device 188, butmay experience an increased amount of time to reach operatingtemperature. In alternate embodiments (not shown), the engine system maypossesses a different number, arrangement, and/or relative processingcapacity of emission control devices. First emission control device 188and second emission control device 190 may include one or more exhaustafter-treatment catalysts configured to catalytically treat the exhaustflow, and thereby reduce an amount of one or more substances in theexhaust flow. For example, one exhaust after-treatment catalyst may beconfigured to trap NO_(x) from the exhaust flow when the exhaust flow islean, and to reduce the trapped NO_(x) when the exhaust flow is rich. Inother examples, an exhaust after-treatment catalyst may be configured todisproportionate NO_(x) or to selectively reduce NO_(x) with the aid ofa reducing agent. In still other examples, an exhaust after-treatmentcatalyst may be configured to oxidize residual hydrocarbons and/orcarbon monoxide in the exhaust flow. Different exhaust after-treatmentcatalysts having any such functionality may be arranged in wash coats orelsewhere in the exhaust after-treatment stages, either separately ortogether. In some embodiments, the exhaust after-treatment stages mayinclude a regenerable soot filter configured to trap and oxidize sootparticles in the exhaust flow.

All or part of the treated exhaust from emission control devices 188 and190 may be released into the atmosphere via exhaust conduit 193.Temperature sensor 191 and flow sensor 192 are coupled to exhaustconduit 193 to monitor operating conditions. Additional sensors (notshown) may be included to detect exhaust pressure, composition, etc.Depending on operating conditions, some exhaust may be diverted insteadto an exhaust inlet passage 116 of a gas mixing tank reservoir 100 viavalve 118. An exhaust inlet port 120 of the gas mixing tank reservoir100 is fluidically coupled with the exhaust inlet passage 116 to permitexhaust gases to flow into the gas mixing tank reservoir 100 (whichherein may be referred to as a mixing tank or flow mixing tank). In thismanner, the flow mixing tank 100 is configured to admit exhaust tappedfrom upstream of first emission control device 188 and downstream of theexhaust manifold 178. The valve 118 may be opened to admit a controlledamount of exhaust gas to the flow mixing tank 100 for desirable tankpressure and gas composition. A check valve 119 is included withinexhaust inlet passage 116 downstream of the valve 118 to reduce thelikelihood of flowing contents of the mixing tank back through exhaustinlet passage 116 towards the exhaust manifold 178. In this way, enginesystem 166 is adapted to accumulate exhaust gases within flow mixingtank 100. The flow mixing tank 100 provides increased homogenization ofthe exhaust gas into the intake air charge. Further, the mixing ofexhaust gas with intake air charge within the flow mixing tank 100provides effective cooling of the exhaust gas for increased availableEGR mass and increased performance.

In engine system 166, compressor 184 is a source of compressed intakeair, but under some conditions, the amount of intake air available fromthe compressor may be inadequate. Such conditions include periods ofrapidly increasing engine load, such as immediately after start-up, upontip-in, or upon exiting deceleration fuel shut-off (DFSO). As such,during a DFSO operation, fuel injection to one or more engine cylindersmay be selectively deactivated responsive to selected vehicledeceleration or braking conditions. During at least some of theseconditions of rapidly increasing engine load, the amount of compressedintake air available from the compressor may be limited due to theturbine not being spun up to a sufficiently high rotational speed (forexample, due to low exhaust temperature or pressure). As such, the timefor the turbine to spin up and drive the compressor to provide an amountof compressed intake air is referred to as turbo lag. During turbo-lag,the amount of torque provided may not match the torque demand, leadingto a drop in engine performance.

In view of the issues noted above, the flow mixing tank 100 of enginesystem 166 may be any reservoir of suitable size configured to storepressurized charge for later discharge. As used herein, the pressurizedcharge refers to the gas stored in flow mixing tank 100. As such, thepressurized charge stored in flow mixing tank 100 may include cleanintake air (e.g., compressed intake air drawn from the intake manifold),combusted exhaust gas (e.g., combusted exhaust gases drawn from theexhaust manifold), or a combination thereof (e.g., a mixture of intakeair and exhaust gas having a defined and controlled EGR percentage). Inone embodiment, the flow mixing tank 100 may be configured to storecharge at the maximum pressure generated by compressor 184. Variousinlets, outlets, and sensors may be coupled to the flow mixing tank 100,as elaborated below. In the embodiment shown in FIG. 1, pressure sensor159 is coupled to the flow mixing tank 100 and configured to respond tothe charge pressure there within. Temperature sensor 139 is also coupledto the flow mixing tank 100 and configured to respond to the temperatureof the charge there within.

In engine system 166, flow mixing tank 100 is selectably coupled tointake system 170, both upstream of compressor 184 and downstream ofcompressor 184. More specifically, the flow mixing tank 100 isconfigured to discharge pressurized charge to the intake system 170,either to a first region upstream of the compressor 184 and downstreamof air cleaner 183, or to a second region downstream of compressor 184and upstream of charge air cooler 185. Discharge to the first region isaccomplished via valve 146 coupled to/within low-pressure exhaust gasrecirculation passage 148 (e.g., LP EGR passage 148), and/or via valve150 coupled to/within surge control passage 152. The LP EGR passage 148and the surge control passage 152 are coupled to the gas mixing tankreservoir 100 via first external split passage 149 (e.g., external to aninterior of the gas mixing tank reservoir 100). Discharge to the secondregion is accomplished via valve 138 coupled to high-pressure exhaustgas recirculation passage 140 (e.g., HP EGR passage 140). Valve 150,valve 146, and valve 138 may be normally closed valves commanded to open(or increase an amount of opening to a position between fully closed andfully open) when a flow of charge from the flow mixing tank to theintake system is desired. In some scenarios, the pressurized charge maybe delivered when the throttle valve is at least partially open. In someembodiments, a pressure recovery cone (not shown) may be fluidicallycoupled between the flow mixing tank and the intake system so thatpressurized charge is conducted through the pressure recovery cone ondischarge from the flow mixing tank. When included, the pressurerecovery cone converts flow energy back to pressure energy during flowconditions by suppressing flow detachment from the conduit walls. Inalternate embodiments, however, the pressure recovery cone may not beincluded.

Flow mixing tank 100 may also be charged with air drawn from the intakesystem, downstream of compressor 184 and upstream of charge air cooler185. More specifically, the flow mixing tank 100 is configured to becharged with compressed intake air from the intake system, drawn fromdownstream of compressor 184 and upstream of intake throttle valve 187,via valve 110 coupled to boost air passage 108. The valve 110 may be anormally closed valve commanded to open (or increase an amount ofopening) when a flow of pressurized intake air charge from the intakesystem to the flow mixing tank is desired. In one example, during lowboost conditions, the valve 110 may be opened to drive at least someintake air pressurized by the compressor into flow mixing tank 100. Asanother example, during high boost conditions, the valve 110 may beopened to drive some compressed intake air into flow mixing tank 100wherein it is mixed with pre-stored combusted exhaust gas to generatehigh pressure EGR. Then, during boosted conditions when a transient EGRrequest is received, the high pressure EGR is discharged into the intakesystem via valve 138 to provide the requested high pressure EGR. A checkvalve 111 coupled upstream of valve 110 allows compressed air from thecompressor to flow into the flow mixing tank under conditions of highthrottle-inlet pressure (TIP) and to be stored therein, but it reducesthe likelihood of flowing stored compressed air back to the compressorunder conditions of low TIP.

Flow mixing tank 100 is also shown selectably coupled to exhaust system172 both upstream and downstream of turbine 186. More specifically, theflow mixing tank 100 is coupled to second external split passage 129 andthe flow of gases from flow mixing tank 100 through second externalsplit passage 129 is adjustable by actuation of three-way valve 130.Three-way valve 130 is coupled to second external split passage 129,first secondary air injection passage 132, and second secondary airinjection (SAI) passage 131. The three-way valve 130 may be normallyclosed to each of the coupled passages (e.g., second external splitpassage 129, first SAI passage 132, and second SAI passage 131) so thatgases do not flow through the three-way valve 130. However, thethree-way valve 130 may be actuated by the controller 169 to allow gasesto flow through the three-way valve 130 from one or more of the coupledpassages.

In a first example, the three-way valve 130 may be actuated (e.g.,opened) to increase the flow of gases from the second external splitpassage 129 into the first SAI passage 132, but reduce the flow of gasesfrom the second external split passage 129 into the second SAI passage131. By opening in this way, the three-way valve 130 allows gases toflow from the flow mixing tank 100 into the exhaust manifold 178,upstream of turbine 186. In a second example, the three-way valve 130may be opened to increase the flow of gases from the second externalsplit passage 129 into the second SAI passage 131 while reducing theflow of gases from first SAI passage 132 into either of the secondexternal split passage 129 or the second SAI passage 131. By opening inthis way, the three-way valve 130 allows gases to flow from the flowmixing tank 100 into the second SAI passage 131. The second SAI passage131 is coupled to turbine bypass passage 135. Gases flow from the flowmixing tank 100, through three-way valve 130, into the second SAIpassage 131, and into the turbine bypass passage 135.

By actuating the three-way valve 130 according to the first exampledescribed above, the flow mixing tank 100 may discharge gases into theexhaust manifold 178 upstream of the turbine 186 (e.g., to heat firstemission control device 188, to spin turbine 186, etc.). By actuatingthe three-way valve 130 according to the second example described above,the flow mixing tank 100 may discharge gases downstream of the turbine186 (e.g., to heat second emission control device 190, to reduce thelikelihood of increasing turbine speed, etc.). Actuation of thethree-way valve 130 may include fully opening or closing the valve toincrease or decrease flow from one or more of the coupled passages fromtraveling through the three-way valve 130. Actuation may also includeincreasing or decreasing an amount of opening of the three-way valve 130to a position between fully open and fully closed in order to increaseor decrease flow from one or more of the coupled passages from travelingthrough the three-way valve 130.

Flow mixing tank 100 may also be charged with combusted exhaust gasesdrawn from the exhaust manifold, upstream of turbine 186. Morespecifically, the flow mixing tank 100 is configured to be charged withcombusted exhaust gases drawn from the exhaust manifold, upstream ofturbine 186, via valve 118. The valve 118 may be a normally closed valvecommanded to open when a flow of combusted exhaust gas from the exhaustmanifold to the flow mixing tank is desired. In one example, during lowboost conditions, or low engine speed-load conditions, the valve 118 maybe opened to drive at least some combusted exhaust gas into flow mixingtank 100. In this way, the EGR percentage of the flow mixing tank chargemay be increased. The check valve 119 coupled downstream of valve 118allows combusted exhaust gas from the exhaust manifold to flow into theflow mixing tank 100 and to be stored therein, but it reduces thelikelihood of exhaust gas from flowing back.

In this way, during a first condition, the flow mixing tank 100 may beselectively charged with intake air from the intake system, downstreamof a compressor, while during a second condition, the flow mixing tankmay be selectively charged with combusted exhaust gas from the exhaustmanifold, upstream of the turbine. During a third condition, the flowmixing tank 100 may be selectively charged with both intake air from theintake system and combusted exhaust gas from the exhaust manifold.

The flow mixing tank 100 includes a plurality of inlet/outlet ports forreceiving and transmitting gases. For example, the flow mixing tank 100includes a boost air port 112 coupled to boost air passage 108, anexhaust inlet port 120 coupled to exhaust inlet passage 116, a first gasoutlet port 144 coupled to first external split passage 149, a secondgas outlet port 136 coupled to HP EGR passage 140, and a third gasoutlet port 128 coupled to second external split passage 129. While theflow mixing tank 100 shown by FIG. 1 includes the above inlet and outletports, alternate embodiments of the flow mixing tank may include adifferent number and/or arrangement of inlet and/or outlet ports.

The flow mixing tank 100 additionally includes a coolant inlet port 164and a coolant outlet port 154 so that the flow mixing tank 100 maytransmit and receive coolant to/from a radiator 161 included within theengine system 166. Coolant flowing through the flow mixing tank 100 mayexchange heat with the gases stored/flowing through the mixing tank. Assuch, the coolant may remove or provide heat to the gases stored withinthe mixing tank depending on a temperature difference between the gasesand coolant. A coolant inlet passage 160 is coupled to both the coolantinlet port 164 of the flow mixing tank 100 and the radiator 161. A valve162 and a temperature sensor 158 are included with (e.g., coupled to)the coolant inlet passage 160. A measurement from temperature sensor 158may be transmitted to the controller 169, and the controller 169 mayactuate valve 162 in order to regulate the flow of coolant throughcoolant inlet passage 160 into the flow mixing tank 100. Coolant maythen flow out of the flow mixing tank 100 through the coolant outletport 154 coupled to a coolant outlet passage 156 to return to theradiator 161. While the radiator 161 is shown coupled to the flow mixingtank 100 in FIG. 1, the radiator may additionally be coupled to othercomponents of the engine system (e.g., the cylinder head 182, or othercomponents not shown by FIG. 1). In other words, the coolant inletpassage 160 and the coolant outlet passage 156 may be passagesperipheral (e.g., secondary) to other coolant passages (not shown)coupled to the radiator.

The flow of the coolant through flow mixing tank 100 may vary dependingon engine conditions, as described in the discussion of FIGS. 3A-3B andFIG. 5 below.

The configuration of flow mixing tank 100 in relation to the engineintake and exhaust systems enables various options for charging anddischarging the flow mixing tank 100. As a first example, such as whenthe engine system is operated in a first mode, the mixing tank may becharged with compressed intake air from the intake system, and thenresponsive to a tip-in (or during high boost conditions), the compressedintake air may be discharged to the intake system to reduce turbo lagand assist in turbine spin-up. As a second example, such as when theengine system is operated in a second mode, the mixing tank may becharged with compressed intake air from the intake system, thecompressed intake air may be discharged to the exhaust manifold to raiseexhaust temperatures and assist in turbine spin-up. As a third example,such as when the engine system is operated in a third mode, the mixingtank may be charged with combusted exhaust gas from the exhaustmanifold, and then during boosted conditions, when EGR is requested, thecombusted exhaust gas may be discharged to the intake system to providethe desired EGR. As a fourth example, such as when the engine system isoperated in a fourth mode, the mixing tank may be charged with combustedexhaust gas from the exhaust manifold, and then responsive to a tip-in,the combusted exhaust gas may be discharged to the exhaust manifold toraise the exhaust pressure upstream of the turbine, and assist inturbine spin-up. In still further examples, the reservoir may be chargedwith at least some combusted exhaust gas and at least some compressedintake air to provide a boost charge of a selected composition (e.g.,desired EGR percentage, desired AFR, etc.) and then, at a later time,the pressurized charge may be discharged to either the intake system(for example, to provide high-pressure EGR, low-pressure EGR, and/orcompressor surge reduction), to the exhaust manifold (for example, toraise the exhaust pressure and/or to provide secondary air injection fornoxious emission reduction), or to the turbine bypass passage (forexample, to expedite catalyst warm-up).

In some embodiments, flow mixing tank 100 may also be charged with theeffluent of one or more unfueled cylinders (that is, charged withunfueled and uncombusted exhaust gas). Specifically, when engine 168 isoperated in DFSO mode, where some of the combustion chambers receive nofuel and merely pump the air admitted through their respective intakevalves, the air pumped and thereby compressed by the unfueled combustionchambers may be drawn from exhaust manifold via valve 118 and stored inmixing tank 100.

In the various engine systems discussed above, and in others fullyconsistent with this disclosure, pressurizing air or an air/exhaustmixture in a mixing tank may cause water vapor to condense inside themixing tank. Therefore in some embodiment, a drain valve (not shown) maybe coupled to flow mixing tank 100. The drain valve may be opened byelectronic control system 167 to drain condensate from the mixing tankonto the road surface below the vehicle in liquid form, or directed tothe exhaust system of the vehicle, evaporated, and discharged as avapor.

The configuration of FIG. 1 enables air stored in the flow mixing tankto be discharged in response to at least a tip-in condition, where thethrottle valve opens suddenly and the compressor is spinning too slowlyto provide the desired intake manifold pressure (MAP). As elaboratedherein below, during at least some tip-in conditions (such as when theboost level at tip-in is lower and anticipated turbo lag is higher),while discharging air from the flow mixing tank, a higher amount ofspark retard may be used to rapidly raise the temperature of exhaust gasand expedite turbine spin-up. During other tip-in conditions (such aswhen the boost level at tip-in is higher and anticipated turbo lag islower), while discharging air from the flow mixing tank, a smalleramount of spark retard (e.g., no spark retard) may be used to provideadditional engine torque (corresponding to the discharged amount ofboost air) to meet the torque demand while the compressor reaches thedesired capacity.

In some embodiments, at least some cylinders of the engine may beconfigured to have spark timing retarded while boost air is dischargedinto the intake system for purposes of heating exhaust gas andexpediting turbine spin. At the same time, other cylinders may beconfigured to maintain ignition timing while boost air is discharged forthe purposes of torque generation. To reduce potential issues arisingfrom a torque differential between the cylinders, the cylinders enablingexhaust gas heating and the cylinder enabling torque generation may beselected based their firing order. In this way, by expediting turbinespin-up, while providing torque, turbo lag can be reduced whileincreasing net engine combustion torque.

The configurations described above enable various methods for providingcharge including air and/or combusted exhaust gas for a combustionchamber of an engine, for spinning up a turbine, for supplying highand/or low-pressure EGR gases to an intake system, for supplyingsecondary air injection to an exhaust manifold and/or turbine bypasspassage, and for supplying gases to a compressor to reduce compressorsurge. Accordingly, some such methods are now described, by way ofexample, with continued reference to the above configuration. It will beunderstood, however, that the methods here described, and others fullywithin the scope of this disclosure, may be enabled via otherconfigurations as well. The methods presented herein include variousmeasuring and/or sensing events enacted via one or more sensors disposedin the engine system. The methods also include various computation,comparison, and decision-making events, which may be enacted in anelectronic control system operatively coupled to the sensors. Themethods further include various hardware-actuating events, which theelectronic control system may command selectively, in response to thedecision-making events.

FIG. 2 shows an embodiment of a gas mixing tank reservoir (such as thegas mixing tank reservoir 100 shown in FIG. 1, which may also bereferred to as a mixing tank, reservoir, or heat exchanger) coupled toan intake system, an exhaust system, and a radiator of an engine system(such as the engine system 166 shown by FIG. 1). The mixing tank 200shown by FIG. 2 includes a housing 202 and a plurality of internalcoolant/gas passages (e.g., internal to the housing 202 of the mixingtank 200). The housing 202 of the embodiment of the mixing tank 200shown by FIG. 2 is formed such that the shape of the mixing tank 200 isapproximately a rectangular parallelepiped. Alternate embodiments mayexist in which the mixing tank possesses a different shape (e.g., thehousing may be cylindrical, etc.), and/or a different arrangement ofsurfaces, and/or a different number of surfaces.

Included within the housing 202 of the mixing tank 200 (e.g., internalto the mixing tank 200) is a coolant manifold 206. The coolant manifold206 includes a plurality of coolant passages internal to the mixing tank200 (e.g., internal to an interior of the mixing tank 200). Also shownby FIG. 2 is a coolant inlet passage 260 (e.g., such as coolant inletpassage 160 shown by FIG. 1) and a coolant outlet passage 256 (e.g.,such as coolant outlet passage 156 shown by FIG. 1). Coolant inletpassage 260 and coolant outlet passage 256 are both external to themixing tank 200 (e.g., external to an interior of the mixing tank 200).Coolant may flow from coolant inlet passage 260 and into a coolant inletport 264 (e.g., such as coolant inlet port 164 shown by FIG. 1) of themixing tank 200. The coolant inlet port 264 includes an aperture (e.g.,opening) in the housing 202 of the mixing tank 200 and permits thetransfer of coolant from the coolant inlet passage 260 into the coolantmanifold 206. In other words, coolant inlet passage 260 is fluidicallycoupled to the coolant inlet port 264, and the coolant inlet port 264 isfluidically coupled with the coolant manifold 206.

The coolant inlet passage 260 includes a valve 262 (e.g., such as valve162 shown by FIG. 1) and a temperature sensor 258 (e.g., such astemperature sensor 158 shown by FIG. 1). The valve 262 may be actuatedby a controller (e.g., such as controller 169 shown by FIG. 1) to adjustthe flow of coolant (e.g., adjust the flow rate or amount of coolant)from the coolant inlet passage 260 to the coolant inlet port 264. Thecontroller (not shown in FIG. 2) may determine the adjustment of theflow of coolant from the coolant inlet passage 260 to the coolant inletport 264 based at least in part on the temperature of the coolant asmeasured and/or detected by temperature sensor 258. In this way, flow ofcoolant to the coolant inlet port 264 may be increased or decreaseddepending on the temperature of the coolant as determined by temperaturesensor 258.

Coolant travels from the coolant inlet passage 260, through the coolantinlet port 264, and into the coolant manifold 206. Coolant flows throughthe plurality of passages included within the coolant manifold 206, andas the coolant flows through the plurality of passages the coolanttransfers thermal energy to and/or from gases contained within gasmixing manifold 204 of the mixing tank 200. In this way, gases withinthe gas mixing manifold 204 of the mixing tank 200 may increase ordecrease in temperature depending on the condition (e.g., temperature)of the coolant flowing through the coolant manifold 206.

The coolant exits the coolant manifold 206 through a coolant outlet port254 (e.g., such as coolant outlet port 154 shown by FIG. 1). The coolantoutlet port 254 includes an aperture (e.g., opening) in the housing 202of the mixing tank 200 and permits the transfer of coolant from thecoolant manifold 206 into the coolant outlet passage 256. In otherwords, the coolant manifold 206 is fluidically coupled to the coolantoutlet port 254, and the coolant outlet port 254 is fluidically coupledto the coolant outlet passage 256.

A radiator (e.g., such as radiator 161 shown by FIG. 1) may routecoolant into the coolant inlet passage 260. Additionally, the coolantoutlet passage 256 may route coolant into the radiator. The gas mixingtank reservoir 200 includes a gas temperature sensor 263 and a gaspressure sensor 259. Measured and/or estimated values for gastemperature and gas pressure may be determined by the temperature sensor263 and pressure sensor 259 (respectively) and utilized by a controller(e.g., such as controller 169 shown by FIG. 1) to control the flow ofcoolant and gases to and from the gas mixing tank reservoir 200 (asdescribed in the discussion of FIGS. 3A-3B and FIGS. 4-5).

According to the arrangement of the coolant manifold 206 and connectingpassages described above, a process of coolant circulation between theradiator and the mixing tank 200 may occur. Coolant may be routed fromthe radiator via coolant inlet passage 260. The flow of coolant fromcoolant inlet passage 260 into the coolant inlet port 264 of the mixingtank 200 is increased or decreased through the actuation of valve 262based on coolant temperature measured and/or detected by temperaturesensor 258. The coolant entering coolant inlet port 264 then passesthrough the plurality of passages included within coolant manifold 206,and an exchange of thermal energy may occur between the coolant and thegases in the gas mixing manifold 204 of the mixing tank 200. The coolantthen exits the mixing tank 200 via the coolant outlet port 254 andenters the coolant outlet passage 256. The coolant outlet passage 256directs the coolant back into the radiator.

The coolant circulation process described above may be a continuousprocess (e.g., magnitude of coolant flow is adjustable within acontinuous range), a binary process (e.g., coolant flow is adjustablefrom on to off, or from off to on), and/or may be selectively configuredto perform as a continuous process or a binary process based on engineconditions.

As mentioned above, the mixing tank 200 includes the gas mixing manifold204 for the storage of gases from an intake system (e.g., such as intakesystem 170 shown by FIG. 1) and/or an exhaust system (e.g., such asexhaust system 172 shown by FIG. 1). Gases from the intake system and/orexhaust system may mix and converge within a plurality of gas passages207 included within the gas mixing manifold 204 and internal to thehousing 202. Also included within the gas mixing manifold 204 is a gasinlet manifold 203 and a gas outlet manifold 205. The gas inlet manifold203 includes passages configured to receive gases from the intake systemand exhaust system. The gas outlet manifold 205 includes passagesconfigured to discharge gases from the flowing mixing tank 200 into theintake system and/or the exhaust system. The gas mixing manifold 204 isfluidically coupled to a plurality of gas inlet ports of the mixing tank200 via the gas inlet manifold 203 and a plurality of gas outlet portsof the mixing tank 200 via the gas outlet manifold 205 to permit thetransfers of gases to and/or from the mixing tank 200.

A boost air passage 208 (e.g., such as boost air passage 108 shown byFIG. 1) is coupled between the mixing tank 200 and an intake manifold ofan engine (e.g., such as intake manifold 176 shown by FIG. 1). The boostair passage 208 is external to an interior of the mixing tank 200. Theboost air passage 208 is fluidically coupled to a boost air port 212(e.g., such as boost air port 112 shown by FIG. 1) of the mixing tank200, and the flow of gases through boost air passage 208 towards boostair port 212 is adjustable by valve 210 (e.g., such as valve 110 shownby FIG. 1). The valve 210 may be actuated by a controller (e.g., such asthe controller 169 shown by FIG. 1) based on engine operatingconditions. The boost air port 212 is fluidically coupled to an internalboost air passage 214 of the mixing tank 200. The internal boost airpassage 214 is internal to an interior of the mixing tank 200. The boostair port 212 includes an aperture (e.g., an opening) within the housing202 of the mixing tank 200 and permits the transfer of intake gases fromthe boost air passage 208 into the internal boost air passage 214.

An exhaust inlet passage 216 (e.g., such as exhaust inlet passage 116shown by FIG. 1) is coupled between the mixing tank 200 and an exhaustmanifold of an engine (e.g., such as exhaust manifold 178 shown by FIG.1). The exhaust inlet passage 216 is external to an interior of themixing tank 200. The exhaust inlet passage 216 is fluidically coupled toan exhaust inlet port 220 (e.g., such as exhaust inlet port 120 shown byFIG. 1) of the mixing tank 200, and the flow of gases through exhaustinlet passage 216 towards the exhaust inlet port 220 is adjustable byvalve 218 (e.g., such as valve 118 shown by FIG. 1).

The exhaust inlet port 220 is fluidically coupled to an internal exhaustinlet passage 222 of the mixing tank 200. The internal exhaust inletpassage 222 is internal to an interior of the mixing tank 200. Theexhaust inlet port 220 includes an aperture (e.g., an opening) withinthe housing 202 of the mixing tank 200 and permits the transfer ofexhaust gases from the exhaust inlet passage 216 into the internalexhaust inlet passage 222.

Internal exhaust inlet passage 222 and internal boost air passage 214merge within an interior of the mixing tank 200 and form an internalintake passage 224. The internal intake passage 224 may receive gasesfrom the intake manifold via internal boost air passage 214, from theexhaust manifold via internal exhaust inlet passage 222, or from boththe intake manifold and the exhaust manifold (via the respectivepassages described above). The internal intake passage 224 isfluidically coupled to the plurality of gas passages within the gasmixing manifold 204. Gases from both the intake manifold and the exhaustmanifold may mix and converge within the internal intake passage 224 andthe plurality of passages within the gas mixing manifold 204.

The plurality of passages within the gas mixing manifold 204 are routedto an internal outlet passage 225. The internal outlet passage 225 isinternal to an interior of the mixing tank 200. The internal outletpassage 225 is coupled to a plurality of gas outlet passages within aninterior of the mixing tank 200 and serves as a connection fortransferring gases from the gas mixing manifold 204 to the gas outletpassages. The embodiment of the mixing tank 200 shown by FIG. 2 includesthree gas outlet passages internal to an interior of the mixing tank(e.g., first internal gas outlet passage 242, second internal gas outletpassage 234, and third internal gas outlet passage 226). Otherembodiments of the mixing tank may include a different number and/orarrangement of gas outlet passages.

The first internal gas outlet passage 242 is coupled between theinternal outlet passage 225 and a first gas outlet port 244 (e.g., suchas first gas outlet port 144 shown by FIG. 1). The first gas outlet port244 is fluidically coupled to a first external split passage 249 (e.g.,such as first external split passage 149 shown by FIG. 1). The firstexternal split passage 249 is external to an interior of the mixing tank200. The first gas outlet port 244 includes an aperture (e.g., anopening) within the housing 202 of the mixing tank 200 and permits thetransfer of gases from the first internal gas outlet passage 242 intothe first external split passage 249.

The first external split passage 249 is fluidically coupled to a surgecontrol passage 252 (e.g., such as surge control passage 152 shown byFIG. 1) and a low-pressure exhaust-gas recirculation passage 248 (e.g.,such as low-pressure exhaust-gas recirculation passage 148 shown by FIG.1). A valve 250 (e.g., such as valve 150 shown by FIG. 1) is includedwithin the surge control passage 252, and a valve 246 (e.g., such asvalve 146 shown by FIG. 1) is included within the low-pressureexhaust-gas recirculation passage 248 (which may herein be referred toas LP EGR passage 248). The valve 250 and the valve 246 may be actuatedby a controller (e.g., controller 169 shown by FIG. 1) to allow gases toflow from the first external split passage 249 into one or both of thesurge control passage 252 and the LP EGR passage 248.

The second internal gas outlet passage 234 is coupled between theinternal outlet passage 225 and a second gas outlet port 236 (e.g., suchas second gas outlet port 136 shown by FIG. 1). The second gas outletport 236 is fluidically coupled to a high-pressure exhaust-gasrecirculation passage 240 (e.g., such as high-pressure exhaust-gasrecirculation passage 140 shown by FIG. 1). The high-pressureexhaust-gas recirculation passage 240 (which may herein be referred toas HP EGR passage 240) is external to an interior of the mixing tank200. The second gas outlet port 236 includes an aperture (e.g., anopening) within the housing 202 of the mixing tank 200 and permits thetransfer of gases from the second internal gas outlet passage 234 intothe HP EGR passage 240. A valve 238 (e.g., such as valve 138 shown byFIG. 1) is included within the HP EGR passage 240. The valve 238 may beactuated by a controller (e.g., controller 169 shown by FIG. 1) to allowgases to flow from the second internal gas outlet passage 234 into theHP EGR passage 240.

The third internal gas outlet passage 226 is coupled between theinternal outlet passage 225 and a third gas outlet port 228 (e.g., suchas third gas outlet port 128 shown by FIG. 1). The third gas outlet port228 is fluidically coupled to a second external split passage 229 (e.g.,such as second external split passage 129 shown by FIG. 1). The secondexternal split passage 229 is external to an interior of the mixing tank200. The third gas outlet port 228 includes an aperture (e.g., anopening) within the housing 202 of the mixing tank 200 and permits thetransfer of gases from the third internal gas outlet passage 226 intothe second external split passage 229.

The second external split passage 229 is fluidically coupled to a firstsecondary air injection passage 232 (e.g., such as first secondary airinjection passage 132 shown by FIG. 1) and a second secondary airinjection passage 231 (e.g., such as second secondary air injectionpassage 131 shown by FIG. 1). A three-way valve 230 (e.g., such asthree-way valve 130 shown by FIG. 1) is fluidically coupled to thesecond external split passage 229, the first secondary air injectionpassage 232 (which may herein be referred to as first SAI passage 232),and the second secondary air injection passage 231 (which may herein bereferred to as second SAI passage 231). The three-way valve 230 may beactuated by a controller (e.g., controller 169 shown by FIG. 1) to allowgases to flow from the second external split passage 229 into one orboth of the first SAI passage 232 and the second SAI passage 231.

In this way, gases may flow from the gas mixing manifold 204 into theinternal outlet passage 225. The gases flowing into the internal outletpassage 225 may then be selectively routed to the first internal gasoutlet passage 242 via the actuation of valve 250 and/or valve 246, thesecond internal gas outlet passage 234 via the actuation of valve 238,and/or the third internal gas outlet passage 226 via the actuation ofthe three-way valve 230.

Gases routed through the first internal gas outlet passage 242 flowthrough the first gas outlet port 244 and into the first external splitpassage 249. The gases flowing through first external split passage 249may be selectively diverted to surge control passage 252 by actuation ofvalve 250, to LP EGR passage 248 by actuation of valve 246, or to bothsurge control passage 252 and LP EGR passage 248 by actuation of valve250 and valve 246 respectively.

Gases routed through the second internal gas outlet passage 234 flowthrough the second gas outlet port 236 and into the HP EGR passage 240.The flow of the gas into the HP EGR passage 240 is controlled byactuation of the valve 238.

Gases routed through the third internal gas outlet passage 226 flowthrough the third gas outlet port 228 and into the second external splitpassage 229. The gases flowing through second external split passage 229may be selectively diverted to first SAI passage 232 and/or second SAIpassage 231 by actuation of three-way valve 230.

As the gases flow through the gas mixing manifold 204 towards theinternal outlet passage 225, the gases may experience an increase ordecrease in thermal energy due to the proximity of the coolant manifold206 with the gas mixing manifold 204. The plurality of passages withinthe coolant manifold 206 are not in fluidic communication with theplurality of passages within the gas mixing manifold 204. In otherwords, no coolant is permitted to enter the passages of the gas mixingmanifold 204, and no exhaust and/or intake gases are permitted to enterthe passages of the coolant manifold 206. However, the passages of thecoolant manifold 206 may be separated from the passages of the gasmixing manifold 204 by a thermally conductive material (e.g., metal) sothat thermal energy is allowed to transfer from one manifold to theother.

In this way, if the temperature of the coolant within the coolantmanifold 206 is lower than the temperature of the gases within the gasmixing manifold 204, thermal energy may transfer from the gases in thegas mixing manifold 204 to the coolant within the coolant manifold 206via the thermally conductive material separating the passages of themanifolds. Similarly, if the temperature of the coolant within thecoolant manifold 206 is higher than the temperature of the gases withinthe gas mixing manifold 204, thermal energy may transfer from thecoolant in the coolant manifold 206 to the gases within the gas mixingmanifold 204 via the thermally conductive material separating thepassages of the manifolds.

The actuation of valve 250, valve 246, valve 238, and three-way valve230 may be controlled at least in part by the temperature of the coolantand/or the temperature of the gases as described in the discussion ofFIGS. 3A-3B below.

FIG. 2 shows an example configuration with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example. Asyet another example, elements shown above/below one another, at oppositesides to one another, or to the left/right of one another may bereferred to as such, relative to one another. Further, as shown in thefigures, a topmost element or point of element may be referred to as a“top” of the component and a bottommost element or point of the elementmay be referred to as a “bottom” of the component, in at least oneexample. As used herein, top/bottom, upper/lower, above/below, may berelative to a vertical axis of the figures and used to describepositioning of elements of the figures relative to one another. As such,elements shown above other elements are positioned vertically above theother elements, in one example. As yet another example, shapes of theelements depicted within the figures may be referred to as having thoseshapes (e.g., such as being circular, straight, planar, curved, rounded,chamfered, angled, or the like). Further, elements shown intersectingone another may be referred to as intersecting elements or intersectingone another, in at least one example. Further still, an element shownwithin another element or shown outside of another element may bereferred as such, in one example.

FIGS. 3A-3B show a method for adjusting a flow of coolant to a gasmixing reservoir (e.g., such as gas mixing tank reservoir 100 shown byFIG. 1, or gas mixing tank reservoir 200 shown by FIG. 2) based on arequest to discharge gas contents from the reservoir and a temperatureof the coolant entering the reservoir. The flow of coolant to the gasmixing tank reservoir 200 may be adjusted in order to adjust thetemperature of the gases contained within (and/or entering) the gasmixing tank reservoir. The temperature of the gases contained within thegas mixing tank reservoir may be adjusted (via adjusting the flow ofcoolant through the gas mixing tank reservoir) to a desired temperaturebased on an indicated location for injecting the gases from thereservoir to one or more of the intake system and exhaust system. Inother words, the temperature of the gases within the gas mixing tankreservoir may be adjusted to a desired temperature by increasing ordecreasing the flow of coolant to the gas mixing tank reservoir, and thedesired temperature of the gases may be based on an intended injectionlocation for the gases in one or both of the intake system and exhaustsystem. In one example, the temperature of the coolant entering the gasmixing tank reservoir may be a measured or estimated coolant temperaturebased on an output of a temperature sensor (e.g., such as thetemperature sensor 258 shown by FIG. 2).

Instructions for carrying out method 300 and the rest of the methodsincluded herein may be executed by a controller based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIG. 1. The controller may employengine actuators of the engine system (e.g., such as valves 162, 146,150, 110, 130, and 118) to adjust engine operation, according to themethods described below.

Turning first to FIG. 3A, method 300 includes estimating and/ormeasuring engine operating conditions at 301 based on one or moreoutputs of various sensors in the engine system and/or operatingconditions of the engine system (e.g., such as various temperaturesensors, pressure sensors, etc., as described above). Engine operatingconditions may include engine speed and load, EGR flow rate (LP and/orHP), mass air flow rate, turbine speed, compressor inlet pressure,emissions control device temperature, coolant flow rate, etc. Theoperating conditions may also include the operating conditions of thegas mixing tank reservoir (e.g., temperature of coolant, temperature ofstored gases, gas pressure, amount of stored gas, percentage of exhaustgas mixed with intake air, etc.).

At 302, the method includes determining if secondary air injection isrequested. For example, based on the measured and/or inferred engineoperating conditions determined at 301, the controller may determinethat providing secondary air injection (SAI) would be advantageous toengine operation (e.g., for reduced emissions, turbine speed increase,etc.). In one example, SAI may be requested in response to one or moreof cold start conditions, an engine temperature below a thresholdtemperature, and a catalyst temperature below a catalyst light offtemperature. In another example, SAI may be requested in response to aconcentration of unburned hydrocarbons in the exhaust (e.g., based on anexhaust air/fuel ratio below a threshold air/fuel ratio indicatingincreased unburned hydrocarbons in the exhaust gas). In yet anotherexample, SAI may be requested in response to a turbine speed of aturbine being below a desired turbine speed (e.g., due to an increase intorque demand such as a tip-in).

The method continues to 304 if SAI is requested by the controller. At304, the method includes determining if the SAI request is based on arequest to increase the turbine speed of the turbine (e.g., based onturbine speed being below a desired turbine speed). As an example, therotational speed of the turbine may be below a desired speed due to asudden increase in engine torque demand (e.g., during a throttle tip-inevent). As a result, an increase in turbine speed may be desired toincrease the output of the compressor of the turbocharger. In thisexample, SAI may be provided to increase the mass flow rate of gasespassing through the exhaust manifold, thereby increasing the flow ratethrough the turbine and increasing turbine rotational speed.

If the SAI request is in response to a low turbine speed (e.g., turbinespeed below a desired turbine speed which may be based on torquedemand), as determined at 304, the method continues to 306 where themethod includes maintaining the coolant flow through the gas mixing tankreservoir at the current level (e.g., not adjusting the coolant flow).As an example, if no coolant is flowing through a coolant manifold(e.g., such as coolant manifold 206 shown by FIG. 2) of the gas mixingtank reservoir when the controller determines that an SAI request is dueto low turbine speed, the gas mixing tank reservoir continues to flow nocoolant through the coolant manifold. As a second example, if coolant isflowing through the coolant manifold of the gas mixing tank reservoir ata determined rate (as determined by one or more sensors) when thecontroller determines that an SAI request is due to low turbine speed,the gas mixing tank reservoir continues to flow coolant through thecoolant manifold at the same rate.

The method continues from 306 at 314 where the method includes providingSAI to the exhaust manifold in order to increase the speed of theturbine. In an example, SAI to the exhaust manifold may be delayed untilan emissions control device reaches operating temperature, as describedfurther in the discussion of FIG. 4 below.

Returning to 304, if the SAI request is not a request to raise turbinespeed, the method continues to 308. One alternative function for SAI isto increase the temperature of one or more emission control devices ifit is determined that the devices are below operational temperature.Another alternative function for SAI is to promote combustion of excesshydrocarbons within exhaust gases. The presence of excess hydrocarbonsmay be based on a measurement of the air-to-fuel ratio of the exhaustgas (as measured by a sensor in the exhaust system). The method at 308includes determining if a temperature of the coolant at the gas mixingtank reservoir (e.g., upstream of and flowing to the gas mixing tankreservoir) is greater than a threshold coolant temperature. Thethreshold coolant temperature may be determined by the controller inresponse to the engine operating conditions measured at 301 and theconfirmation of an SAI request at 302. In one example, the thresholdcoolant temperature may be based on the temperature of the exhaust gasexiting the exhaust manifold and/or the temperature of the intake airentering (or contained within) the gas mixing tank reservoir. Saidanother way, the threshold temperature may be based on a temperature ofgases stored within the gas mixing tank reservoir.

If the determined coolant temperature is not greater than the thresholdcoolant temperature as determined at 308, the method continues to 310where the method includes not circulating coolant to (or decreasing theflow of coolant to) the gas mixing tank reservoir. For example, ifcoolant is currently flowing to the gas mixing tank reservoir, themethod at 310 may include stopping (or decreasing) coolant flow to themixing tank reservoir. However, if coolant is currently not flowing tothe gas mixing tank reservoir before 310, the method at 310 may includemaintaining no coolant flow to the gas mixing tank reservoir. The flowof coolant to the gas mixing tank reservoir may be stopped (ordecreased) by actuation of a valve (e.g., such as valve 262 shown byFIG. 2) in a coolant passage upstream of the gas mixing tank reservoir,as described in the discussion of FIG. 2. In another example, the methodat 310 may include decreasing the flow of coolant (e.g., via decreasingan amount of opening of the valve) to the gas mixing tank reservoir. Inmethod 300, wherever the method includes circulating or not circulatingcoolant to the gas mixing tank reservoir, the method may insteadincluding increasing the flow of coolant (from a current level deliveredto the gas mixing tank reservoir) or decreasing the flow of coolant(from the current level). In this way, these methods may includeadjusting the coolant valve mentioned above into a plurality ofpositions between fully open (to flow coolant at a maximum flow rate) ora fully closed (to stop coolant flow altogether) position.

The method then continues to 314 where the method includes providing therequested SAI via the gas mixing tank reservoir. In one example, themethod at 314 may include delaying providing the requested SAI until thegas temperature of gases within the gas mixing tank reservoir are at adesired injection temperature for the SAI request. For example, SAI maybe delayed until the temperature of gases within the gas mixing tankreservoir increases (e.g., due to decreased coolant flow) to a leveldesired for SAI.

Returning to 308, if the determined coolant temperature is greater thanthe threshold temperature, the method continues to 312 where the methodincludes circulating coolant through the gas mixing tank reservoir (orincreasing the flow of coolant to the gas mixing tank reservoir). Asexplained above, the threshold temperature may be based on thetemperature of gases within the mixing tank reservoir and/or thetemperature of the intake air entering (or contained within) the gasmixing tank reservoir. If the temperature of the coolant is higher thanthe threshold temperature (e.g., the temperature of the intake air),coolant is circulated through the gas mixing tank reservoir in order toincrease the temperature of the intake air within the reservoir. Theincrease temperature of the intake air allows for a more efficientcombustion of unburned hydrocarbons and an expedited increase inemission control device temperature, as described above. The method thencontinues to 314 to provide the requested SAI. In one example, themethod at 314 may include delaying providing the requested SAI until thegas temperature of gases within the gas mixing tank reservoir are at adesired injection temperature for the SAI request. For example, SAI maybe delayed until the temperature of gases within the gas mixing tankreservoir increase (e.g., due to increased coolant flow) to a leveldesired for SAI. The method at 314 then includes delivering therequested SAI when the gas temperature is at the desired injectiontemperature.

If SAI is not requested at 302, or if SAI is provided at 314, the methodcontinues to 316 where the method includes determining if compressorsurge is expected and/or detected. The determination of the condition ofthe compressor may be based a difference in pressure between thecompressor inlet and outlet, the intake air flow rate through thecompressor, etc. The pressure and flow rate at the inlet and outlet ofthe compressor may be measured by one or more sensors at the compressorand/or intake manifold (e.g., such as manifold air pressure sensor 175).The compressor and/or intake manifold may also include one or moretemperature sensors, flow sensors, etc.

If compressor surge is expected and/or detected based on the outputs ofthe various sensors (as described above) and/or additional engineoperating conditions, the method continues to 318. At 318, the methodincludes determining if the temperature of the coolant entering (orflowing to) the gas mixing tank reservoir is greater than a thresholdcoolant temperature. The threshold coolant temperature may be determinedby the controller based on the engine operating conditions determined at301 and the expectation and/or detection of compressor surge at 316. Inone example, the threshold temperature may be based on the temperatureof the gases contained within the gas mixing tank reservoir.

If the coolant temperature is not greater than the threshold temperatureat 318, the method continues to 322 where the method includes notcirculating coolant to and through the gas mixing tank reservoir (oralternatively, as explained above, decreasing the flow of coolant to thegas mixing tank reservoir). For example, if the threshold temperature isbased on the temperature of the gases contained within the gas mixingtank reservoir and the coolant temperature is less than the gastemperature within the reservoir, coolant may not be circulated so thatthe temperature of the gases within the reservoir do not decreasefurther. Instead, the temperature of the gases within the gas mixingtank reservoir may increase. The higher temperature of the gases withinthe reservoir provides a greater increase in pressure at the compressorinlet when the gases are discharged into the compressor inlet. Themethod then continues to 324 where the stored charge within the gasmixing tank reservoir is discharged into an intake passage, upstream ofthe compressor inlet, to increase the pressure and/or flow at thecompressor inlet. In this way, providing gasses to the compressor inletfrom the gas mixing tank reservoir may reduce compressor surge. In oneexample, the method at 324 may include delaying the discharge upstreamof the compressor inlet until the gas temperature of gases within thegas mixing tank reservoir are at a desired injection temperature for thedischarge request. For example, the discharge may be delayed until thetemperature of gases within the gas mixing tank reservoir increase(e.g., due to decreased coolant flow) to a level desired for dischargeupstream of the compressor inlet to reduce compressor surge. The methodat 324 then includes delivering the requested discharge when the gastemperature is at the desired injection temperature.

If the coolant temperature is determined to be above the thresholdtemperature at 318, the method instead continues to 320 where the methodincludes circulating coolant (or increasing coolant flow) to the gasmixing tank reservoir. For example, if the threshold temperature isbased on the temperature of the gases contained within the gas mixingtank reservoir, coolant is circulated so that the temperature of thegases within the reservoir increases. The higher temperature of thegases within the reservoir provides a greater increase in pressure atthe compressor inlet when the gases are discharged into the compressorinlet. The method then continues to 324 where the stored charge withinthe gas mixing tank reservoir is discharged upstream of the compressorinlet to increase the pressure and/or flow at the compressor inlet. Inone example, the method at 324 may include delaying the dischargeupstream of the compressor inlet until the gas temperature of gaseswithin the gas mixing tank reservoir are at a desired injectiontemperature for the discharge request. For example, the discharge may bedelayed until the temperature of gases within the gas mixing tankreservoir increase (e.g., due to increased coolant flow) to a leveldesired for discharge upstream of the compressor inlet to reducecompressor surge. The method at 324 then includes delivering therequested discharge when the gas temperature is at the desired injectiontemperature.

If compressor surge is not expected and/or detected at 316, or if storedair is discharged upstream of the compressor at 324, the methodcontinues to 326. At 326, the method includes determining iflow-pressure exhaust-gas recirculation (LP EGR) is requested. In oneexample, the controller may determine that LP EGR is requested based onone or more engine operating conditions. The method at 324 may furtherinclude determining if an increase in LP EGR is requested and/ordetermining a desired percentage of LP EGR that is requested. Thedetermination at 326 may be in response to one or more of operatingconditions of the gas mixing tank reservoir (e.g., amount of chargestored), conditions at the compressor (e.g., condensate formingconditions at the compressor inlet), etc.

If LP EGR is requested at 326, the method continues to 328 where themethod includes determining if the temperature of the coolant enteringthe gas mixing tank reservoir is greater than a threshold coolanttemperature. The threshold coolant temperature may be determined by thecontroller in response to the engine operating conditions measured at301 and the operating conditions of the gas mixing tank reservoir (e.g.,temperature of the gases contained within the reservoir, flow of gasesthrough the reservoir, etc.). In one example, the threshold temperaturemay be based on the temperature of the gases contained within the gasmixing tank reservoir.

If the coolant temperature is determined to be above the thresholdtemperature at 328, the method continues to 330 where the methodincludes determining whether condensate formation (e.g., the amount ofcondensate) at the compressor inlet is greater than a condensatethreshold. The condensate threshold may be based on an amount ofcondensate that may result in degradation of the compressor. Forexample, condensate at the compressor inlet can cause corrosion anddegradation of the compressor wheel when the amount of condensate isabove a threshold value. The amount of condensate at the compressorinlet may change based on a variety of conditions such as ambienttemperature of the atmosphere (e.g., temperature of the intake air), thehumidity of the intake air, the temperature of any EGR gases injectedupstream of the compressor, etc.

If the amount of condensate at the compressor inlet determined at 330 isbelow the condensate threshold, the method continues to 336 where themethod includes not circulating coolant (or decreasing the flow rate oramount of coolant flowing) to the gas mixing tank reservoir. As anexample, the condensate at the compressor inlet may be at an acceptablelevel for continued operation of the compressor. Additionally, thetemperature of the coolant at the gas mixing tank reservoir is above thethreshold temperature based on the temperature of the gases containedwithin the mixing tank. In response to these conditions, the controllerdoes not circulate coolant through the mixing tank in order to reducethe thermal energy transferred to the gases stored within the tank fromthe coolant.

The method then continues to 338, where the method includes providingthe desired percentage of EGR (e.g., desired amount of EGR), from thegas mixing tank reservoir, upstream of the compressor in the intakesystem to provide LP EGR. The percentage of LP EGR injected into theintake system may be determined in part by the ratio of exhaust gas tointake gas within the gas mixing tank reservoir. By reducing thecirculation of coolant within the mixing tank at 336 prior to thedischarge of the gases at 338, the gases may be injected at a lowertemperature than if coolant had been circulated.

Returning to 330, if the amount of condensate at the compressor isdetermined to be above the condensate threshold, the method continues to332 where the method includes circulating coolant through the gas mixingtank reservoir (or increasing the coolant flow to the gas mixing tankreservoir). Circulating coolant through the gas mixing tank reservoirmay raise the temperature of the gases stored within the tank prior toinjection into the intake system upstream of the compressor.

The method then continues to 338, where the method includes providingthe desired percentage of LP EGR upstream of the compressor in theintake system from the gas tanking mixing reservoir. The amount of gasesinjected into the intake system from the reservoir may be determined inpart by the ratio of exhaust gas to intake gas within the gas mixingtank reservoir and the desired percentage of LP EGR. By allowing thecirculation of coolant within the mixing tank at 332 prior to thedischarge of the gases at 338, the gases may be injected at a highertemperature than if coolant had not been circulated. The highertemperature gases may reduce the formation of condensation at thecompressor inlet. In one example, the method at 338 may include delayingproviding the requested LP EGR injection until the gas temperature ofgases within the gas mixing tank reservoir are at a desired injectiontemperature for the LP EGR request. For example, LP EGR injection may bedelayed until the temperature of gases within the gas mixing tankreservoir increase (e.g., due to increased coolant flow) to a leveldesired for LP EGR. The method at 338 then includes delivering therequested LP EGR when the gas temperature is at the desired injectiontemperature.

Returning to 328, if the coolant temperature is determined to be belowthe threshold temperature, the method continues to 334 where the methodincludes determining whether the amount of condensate at the compressorinlet is greater than a condensate threshold. The condensate thresholdmay be based on an acceptable level of condensate for compressoroperation, as described in the discussion of 330 above.

If the amount of condensate at the compressor inlet determined at 334 isbelow the condensate threshold, the method continues to 332 where themethod includes circulating coolant (or increases the flow rate oramount of coolant flowing) to the gas mixing tank reservoir. As anexample, the condensate at the compressor inlet may be at an acceptablelevel for continued operation of the compressor. Additionally, thetemperature of the coolant at the gas mixing tank reservoir is below thethreshold temperature based on the temperature of the gases containedwithin the mixing tank. In response to these conditions, the controllercirculates coolant through the mixing tank in order to reduce thetemperature and increase the density of the gases contained within thegas mixing tank reservoir.

The method then continues to 338, where the method includes providingthe desired percentage of EGR (e.g., desired amount of EGR) from the gasmixing tank reservoir, upstream of the compressor in the intake systemto provide LP EGR. The percentage of LP EGR injected into the intakesystem may be determined in part by the ratio of exhaust gas to intakegas within the gas mixing tank reservoir. By increasing the circulationof coolant within the mixing tank at 332 prior to the discharge of thegases at 338, the gases may be injected at a lower temperature than ifcoolant had not been circulated.

Returning to 334, if the amount of condensate at the compressor inletdetermined at 334 is above the condensate threshold, the methodcontinues to 336 where the method includes not circulating coolant tothe gas mixing tank reservoir (or decreasing the coolant flow to the gasmixing tank reservoir). Not circulating coolant through the gas mixingtank reservoir may increase the temperature of the gases containedwithin the gas mixing tank reservoir prior to injection into the intakesystem upstream of the compressor.

The method then continues to 338, where the method includes providingthe desired percentage of LP EGR upstream of the compressor into theintake system from the gas mixing tank reservoir. The amount of gasesinjected into the intake system from the reservoir may be determined inpart by the ratio of exhaust gas to intake gas within the gas mixingtank reservoir and the desired percentage of LP EGR. By reducing thecirculation of coolant within the mixing tank at 336 prior to thedischarge of the gases at 338, the gases may be injected at a highertemperature than if coolant circulation had not been reduced. The highertemperature gases may reduce the formation of condensation at thecompressor inlet. In one example, the method at 338 may include delayingproviding the requested LP EGR injection until the gas temperature ofgases within the gas mixing tank reservoir are at a desired injectiontemperature for the LP EGR request. For example, LP EGR injection may bedelayed until the temperature of gases within the gas mixing tankreservoir increase (e.g., due to increased coolant flow) to a leveldesired for LP EGR. The method at 338 then includes delivering therequested LP EGR when the gas temperature is at the desired injectiontemperature.

If LP EGR is not requested at 326, or if the determined percentage of LPEGR is provided at 338, the method 300 continues to 340 shown by FIG.3B, where the method includes determining if high-pressure exhaust-gasrecirculation (HP EGR) is requested in response to the estimated and/orinferred conditions at 301. The determination at 340 may be partly inresponse to operating conditions of the gas mixing tank reservoir (e.g.,amount of charge stored).

If HP EGR is requested at 340, the method continues to 342 where themethod includes determining if the temperature of the coolant enteringthe gas mixing tank reservoir is greater than a threshold coolanttemperature. The threshold coolant temperature may be determined by thecontroller in response to the engine operating conditions measured at301 and the operating conditions of the gas mixing tank reservoir (e.g.,temperature of the gases contained within the reservoir, flow of gasesthrough the reservoir, etc.). In one example, the threshold temperaturemay be based on the temperature of the gases contained within the gasmixing tank reservoir.

If the determined coolant temperature is not greater than the thresholdtemperature at as determined at 342, the method continues to 346 wherethe method includes circulating coolant (or increasing the flow rate oramount of coolant flowing) to the gas mixing tank reservoir. Asexplained above, the threshold temperature may be based on thetemperature of the gases contained within the gas mixing tank reservoirand/or the temperature of intake gases entering (or contained within)the gas mixing tank reservoir. If the temperature of the coolant islower than the threshold temperature, coolant is circulated so that thetemperature of the gases within the reservoir decreases. The lowertemperature of the gases enables an increased amount of charge to bestored within the reservoir at a pressure appropriate for dischargingdownstream of the compressor. The coolant may also be circulated inorder to reduce the temperature of hot exhaust gases entering the gasmixing tank reservoir in order to decrease degradation of the mixingtank and/or the intake system.

The method then continues to 348 where the method includes dischargingthe charge within the gas mixing tank reservoir downstream of thecompressor outlet in order to provide the desired amount of HP EGR gasesto the intake system. In one example, the method at 348 may includedelaying providing the requested HP EGR injection until the gastemperature of gases within the gas mixing tank reservoir are at adesired injection temperature for the HP EGR request. For example, HPEGR injection may be delayed until the temperature of gases within thegas mixing tank reservoir decrease (e.g., due to increased coolant flow)to a level desired for HP EGR. The method at 338 then includesdelivering the requested HP EGR when the gas temperature is at thedesired injection temperature.

Returning to 342, if the determined coolant temperature is greater thana threshold temperature, the method continues to 344 where the methodincludes not circulating coolant to the gas mixing tank reservoir (orthe flow of coolant to the gas mixing tank reservoir is decreased). Asexplained above, the threshold temperature may be based on thetemperature of the gases contained within the gas mixing tank reservoirand/or the temperature of the intake air entering (or contained within)the gas mixing tank reservoir. If the temperature of the coolant isgreater than the threshold temperature, coolant is not circulated sothat the temperature of the gases within the reservoir does notincrease. The lower temperature of the gases enables an increased amountof charge to be stored within the reservoir at a pressure appropriatefor discharging downstream of the compressor, and may reduce degradationof system components, as described above.

The method then continues to 348 where the method includes dischargingthe charge within the gas mixing tank reservoir downstream of thecompressor outlet in order to provide the desired amount of HP EGR gasesto the intake system. In one example, the method at 348 may includedelaying providing the requested HP EGR injection until the gastemperature of gases within the gas mixing tank reservoir are at adesired injection temperature for the HP EGR request. For example, HPEGR injection may be delayed until the temperature of gases within thegas mixing tank reservoir decrease (e.g., due to decreased coolant flow)to a level desired for HP EGR. The method at 338 then includesdelivering the requested HP EGR when the gas temperature is at thedesired injection temperature.

If HP EGR is not requested at 340, or if the determined percentage of HPEGR is provided at 348, the method continues to 350 where the methodincludes determining if there is an opportunity to store charge from theintake system and/or the exhaust system at the gas mixing tankreservoir. The determination at 350 may be partly in response tooperating conditions of the gas mixing tank reservoir (e.g., amount ofcharge stored). In one example, reservoir charging conditions may bepresent if the gas mixing tank reservoir is sufficiently empty (e.g.,gas mixing tank reservoir pressure being lower than a threshold). Inanother example, a storage opportunity may include a decrease in chargedemand as described by the method 300 (e.g., a decrease in demand forSAI, compressor surge reduction, LP EGR, and/or HP EGR). As anotherexample, reservoir charging conditions may be present if the engine isoperating at a sufficiently high boost level (e.g., operating with boostat higher than a threshold level). As yet another example, reservoircharging conditions may be confirmed during an engine deceleration fuelshut-off operation. As still another example, reservoir chargingconditions may be confirmed during a transient following a tip-outevent. A storage opportunity may also include a condition in which oneor more discharge requests are activated by the controller, with thepotential inflow of gases into the gas mixing tank reservoir from theintake or exhaust systems being greater than the demand for outflow fromthe mixing tank. In such an example, the gas mixing tank reservoir mayaccumulate charge while simultaneously discharging a percentage of totalcharge to one or both of the intake system or the exhaust system. Inother words, under some conditions, the gas mixing tank reservoir may becapable of accumulating charge faster than it disperses charge. Suchsituations can be considered storage opportunities. As such, based onengine operating conditions at the time the charging opportunity isconfirmed, it may be determined whether the charge the gas mixing tankreservoir with compressed air from the intake manifold and/or combustedexhaust gas from the exhaust manifold.

Gas mixing tank reservoir conditions may be estimated using one or moresensors coupled to the reservoir, such as pressure, temperature, andair-fuel ratio sensors, as described above with reference to 301.However, in other examples, one or more gas mixing tank reservoirconditions may be inferred or retrieved from a memory of the controllerrather than being sensed per se. For example, where the gas mixing tankreservoir was previously charged using air from the intake system, basedon compressor conditions, intake air temperature and pressureconditions, as well as EGR demands at the time of charging, a state ofthe charge in the gas mixing tank reservoir may be inferred. As anotherexample, where the gas mixing tank reservoir was previously charged withcombusted exhaust gas from the exhaust manifold, based on engineoperating conditions, exhaust conditions, and EGR demands at the time ofcharging, a state of the charge in the gas mixing tank reservoir may beinferred. Likewise, where the gas mixing tank reservoir was previouslydischarged to the intake system, based on the duration of discharging aswell as boost conditions during the discharging, a state of charge (ifany) remaining in the gas mixing tank reservoir may be inferred. In thesame way, where the gas mixing tank reservoir was previously dischargedto the exhaust manifold, based on the duration of discharging as well asengine conditions during the discharging, a state of charge (if any)remaining in the gas mixing tank reservoir may be inferred.

Based on the estimated conditions, it may be determined if a gas mixingtank reservoir charging opportunity is present. In one example,reservoir charging conditions may be present if the gas mixing tankreservoir is sufficiently empty (e.g., gas mixing tank reservoirpressure being lower than a threshold). As another example, reservoircharging conditions may be present if the engine is operating at asufficiently high boost level (e.g., operating with boost at higher thana threshold level). As yet another example, reservoir chargingconditions may be confirmed during an engine DFSO operation. As stillanother example, reservoir charging conditions may be confirmed during atransient following a tip-out event. As such, based on engine operatingconditions at the time the charging opportunity is confirmed, it may bedetermined whether the charge the gas mixing tank reservoir withcompressed air from the intake system and/or combusted exhaust gas fromthe exhaust manifold. For example, as elaborated below, the gas mixingtank reservoir may be selectively charged based on engine speed, vehiclespeed, manifold pressure, etc. at the time of the charging opportunity.

If at 350 a storage opportunity is not available, the method continuesto 354 where the method includes not charging the gas mixing tankreservoir with one or more of fresh air from the intake system andcombusted gas from the exhaust system. In other words, the gas mixingtank reservoir is not charged with gases from either the intake systemor the exhaust system.

If at 350 a storage opportunity is available, the method continues to352 where the method includes charging the gas mixing tank reservoirwith one or more of fresh air from the intake system and combustedexhaust gas from the exhaust system. In other words, the gas mixing tankreservoir is charged with gases from one or both of the intake systemand the exhaust system.

By charging the gas mixing tank reservoir with combusted exhaust gasfrom the exhaust manifold, exhaust energy may be pre-stored in thereservoir and discharged at a later time to either provide EGR (whendischarged into the intake system) or raise exhaust pressure (whendischarged into the exhaust manifold). By charging the gas mixing tankreservoir with pressurized intake air from the intake system, boostenergy may be pre-stored in the reservoir and discharged at a later timeto raise exhaust pressure (when discharged into the exhaust manifold).In particular, turbine energy can be increased by increasing thepre-turbine exhaust pressure. In each case, by storing charge in the gasmixing tank reservoir for use at a later time, boosted engineperformance can be increased.

A valve (e.g., such as valve 210 shown by FIG. 2) fluidically coupled toa boost air port (e.g., such as boost air port 212 shown by FIG. 2) ofthe reservoir may be opened for a duration to charge the reservoir withcompressed intake air from the intake system, and/or a valve (e.g., suchas valve 218 shown by FIG. 2) fluidically coupled to an exhaust inletport (e.g., such as exhaust inlet port 220 shown by FIG. 2) of thereservoir may be opened for a duration to charge the reservoir withexhaust gas from the exhaust manifold. A duration of opening of theintake charge valve and/or the exhaust charge valve may be adjusted toadjust the composition of charge stored in the reservoir so as toprovide a desired gas mixing tank reservoir charge EGR percentage (ordilution). In one example, the gas mixing tank reservoir may be chargedwith air and combusted exhaust gas to provide charge of a desired EGRpercentage and desired pressure, such that when the pressurized chargeis eventually discharged during a subsequent boosted engine operation,high pressure EGR can be enabled.

For example, during a first condition, when a tip-in is predicted athigh engine speeds, the gas mixing tank reservoir may be charged withcombusted exhaust gases. Herein, the engine may be operating at higherengine speeds with a pedal position near a closed position and with avehicle speed being higher than a threshold speed but with an exhaustpressure being greater than a threshold pressure. In comparison, duringa second condition, when a tip-in is predicted at low engine speeds, thegas mixing tank reservoir may be charged with fresh intake air andcombusted exhaust gases, with a ratio of the fresh intake air tocombusted exhaust gases adjusted based on a desired gas mixing tankreservoir EGR percentage.

During some conditions, the gas mixing tank reservoir may be chargedwith a first amount of combusted exhaust gas at a first, lower pressurefrom the exhaust manifold, upstream of the turbine. This initialcharging increases the EGR percentage of the reservoir charge but thestored exhaust gas is at a lower pressure. To further raise the pressureof the stored charge, the gas mixing tank reservoir may be subsequentlyfurther charged with a second amount of fresh intake air at a second,higher pressure from the intake system, downstream of the compressor.This later charging slightly decreases the EGR percentage of thereservoir charge but raises the charge pressure. The first and secondamounts may be adjusted to provide a desired EGR percentage of thepressurized charge. The stored charge can then be advantageouslydischarged during selected boosted engine conditions to provide highpressure EGR benefits.

As another example, the gas mixing tank reservoir may be charged with atleast some combusted exhaust gases (e.g., with only combusted exhaustgases) during a tip-out at lower engine speeds. In comparison, during atip-out at higher engine speeds, the controller may charge the gasmixing tank reservoir with at least some compressed intake air from theintake system (e.g., with only compressed intake air). As yet anotherexample, when charging conditions are confirmed during an engine DFSOoperation, the reservoir may be charged with uncombusted exhaust gasreleased from the cylinders having fuel shut-off.

As such, following the charging, gas mixing tank reservoir conditionsmay be updated in the controller's memory. In one example, gas mixingtank reservoir conditions may be updated using one or more sensorscoupled to the reservoir, such as pressure, temperature, and air-fuelratio sensors. However, in other examples, gas mixing tank reservoirconditions may be inferred and updated in the memory of the controllerrather than being sensed per se. For example, where the gas mixing tankreservoir was recently charged using air from the intake system, basedon compressor conditions, intake air temperature and pressureconditions, as well as EGR demands at the time of charging, a state ofthe charge in the gas mixing tank reservoir may be inferred and updated.As another example, where the gas mixing tank reservoir was currentlycharged with combusted exhaust gas from the exhaust manifold, based onengine operating conditions, exhaust conditions, and EGR demands at thetime of charging, a state of the charge in the gas mixing tank reservoirmay be inferred and updated.

In one example, the EGR percentage of the gas mixing tank reservoir maybe estimated or inferred based on one or more an exhaust air-fuel ratiosensor output, MAF, and a fuel injector pulse-width. The controller maybe configured to estimate a volume of gas that was stored in thereservoir based on a gas mixing tank reservoir pressure. The controllermay then estimate how much of that volume was air based on MAF changesfollowing discharging of the pressurized charge, and how much of thatvolume included fuel based on fuel injection adjustments followingdischarging of the pressurized charge (e.g., based on a fuel injectorpulse-width). An air-to-fuel ratio estimated may then be based on theair and fuel estimates. In an alternate example, the estimatedair-to-fuel ratio may be based on the output of an intake oxygen sensor.The estimated air-to-fuel ratio may then be compared to a measuredair-to-fuel ratio to map an error. The error may then be used to updatean EGR percentage estimate of the gas mixing tank reservoir charge. Thestored gas mixing tank reservoir conditions may be retrieved by thecontroller during a subsequent discharging operation. It will beappreciated that in all cases, the charging may be performed during anengine cycle preceding a tip-in event where the pressurized charge isdischarged.

In this way, a gas mixing tank reservoir may be selectively charged withone or more of fresh intake air from an intake system and combustedexhaust gas from an exhaust manifold. The charging with fresh intake airand combusted exhaust gas may be performed to enable storing of a gasmixing tank reservoir charge having a selected EGR percentage. Followingthe selective charging, such as in response to a tip-in, the pressurizedcharge may be discharged from the gas mixing tank reservoir to theintake system and/or the exhaust manifold, based on engine operatingconditions at the time of the tip-in, to thereby reduce turbo lag andincrease boosted engine performance.

FIG. 4 shows a method 400 for discharging gas contents of a gas mixingtank reservoir (e.g., such as gas mixing tank reservoir 100 shown byFIG. 1, or gas mixing tank reservoir 200 shown by FIG. 2) as secondaryair injection into either an exhaust manifold or a turbine bypasspassage around a turbine based on engine operating conditions. In oneexample, the engine operating conditions may include a measurement orestimate of the temperature of a first emission control device (e.g.,such as the first emission control device 188 shown by FIG. 1), ameasurement or estimate of the temperature of a second emission controldevice (e.g., such as the second emission control device 190 shown byFIG. 1), and a measurement or estimate of the rotational speed of aturbine (e.g., such as turbine 186 shown by FIG. 1). As described duringthe discussion of FIG. 1, the first emission control device and thesecond emission control device may include one or more exhaustafter-treatment catalysts configured to catalytically treat the exhaustflow, and thereby reduce an amount of one or more substances in theexhaust flow. In an example arrangement (referenced by method 400 belowand shown schematically by FIG. 1), the first emission control device ispositioned upstream of an exhaust turbine, and the second emissioncontrol device is positioned downstream of the exhaust turbine.

At 401, the method includes estimating and/or measuring engine operatingconditions based on outputs of one or more temperature sensors, pressuresensors, etc. and/or one or more additional engine operating conditions.The engine operating conditions may further include engine speed andload, EGR flow rate (LP and/or HP), mass air flow rate, compressor inletpressure, coolant flow rate, and/or other parameters based onmeasurements from sensors within an engine system. The engine operatingconditions may also include the operating conditions of a gas mixingtank reservoir (e.g., temperature of coolant, gas pressure, amount ofstored gas, percentage of exhaust gas mixed with intake air, etc.).

At 402, the method includes determining if the temperature of the firstemission control device is greater than a temperature threshold. Forexample, the threshold temperature may be based on an operatingtemperature at which the emissions control device can efficiently removehydrocarbons and/or other noxious compounds from exhaust gas. In anotherexample, the threshold temperature may be a catalyst light offtemperature of the first emission control device.

If the temperature of the first emission control device is not greaterthan the temperature threshold at 402, the method continues to 404 wherethe method includes increasing the flow of secondary air injection (SAI)to the exhaust manifold. In one example, the method at 404 may includethe controller actuating a valve in a passage between the gas mixingtank reservoir and the exhaust manifold to increase the amount of SAIflowing to the exhaust manifold from the gas mixing tank reservoir. Thismay result in the combustion of unburned hydrocarbons in the exhaustgas, thereby increasing the thermal energy of the exhaust gas andincreasing the temperature of the first emission control device.

If the temperature of the first emission control device is higher thanthe temperature threshold at 402, the method continues to 406. At 406,the method includes determining whether the rotational speed of theturbine is greater than a threshold value. For example, the thresholdvalue may be based on a desired compressor flow output for supplyingcharge air to the engine and/or the gas mixing tank reservoir. Thethreshold value may also be based on driver torque demand (e.g., basedon a throttle position or accelerator pedal position).

If the turbine rotational speed determined at 406 is not greater thanthe threshold value, the method continues to 404 where the methodincludes increasing secondary air injection (SAI) to the exhaustmanifold from the gas mixing tank reservoir, as explained above. In thisway, the increased airflow to the exhaust system (e.g., exhaust passage)upstream of the turbine may increase the turbine speed, therebyincreasing rotation of the compressor and delivering demanded torque.

At 406, if the turbine rotational speed is greater than the thresholdvalue, the method continues to 408. At 408, the method includesdetermining whether the temperature of the second emission controldevice is greater than a threshold temperature. For example, thethreshold temperature may be based on an operating temperature at whichthe second emission control device can efficiently remove hydrocarbonsand/or other noxious compounds from exhaust gas. In one example, thethreshold temperature may be a catalyst light off temperature for thesecond emission control device.

If the temperature of the second emission control device is not greaterthan the temperature threshold at 408, the method continues to 410 wherethe method includes increasing the flow of secondary air injection (SAI)to a turbine bypass passage arranged around the turbine. In one example,the method at 410 includes the controller actuating a valve in a passagebetween the gas mixing tank reservoir and the turbine bypass passage toincrease the amount of SAI routed to the turbine bypass passage from thegas mixing tank reservoir in order to combust unburned hydrocarbons inthe exhaust gas, thereby increasing the thermal energy of the exhaustgas and increasing the temperature of the second emission controldevice.

If the temperature of the second emission control device is higher thanthe temperature threshold at 408, the method continues to 412 where themethod includes decreasing the amount of SAI delivered to the exhaustmanifold and/or the turbine bypass from the gas mixing tank reservoir.For example, if the first emission control device is above the thresholdtemperature at 402, the turbine is above the threshold rotational speedat 406, and the second emission control device is above the thresholdtemperature at 412, the controller may actuate one or more valvesdisposed in passages between the gas mixing tank reservoir and theexhaust system to decrease secondary air injection. This may result inconserving charge within the gas mixing tank reservoir and/or directingcharge to the intake system instead of the exhaust system.

In an example routine, the exhaust manifold may receive SAI gases untila first emission control device reaches operating temperature. Theexhaust manifold may then continue to receive SAI gases until a desiredturbine rotational speed is achieved. Once the first emission controldevice reaches operating temperature and the turbine reaches the desiredrotational speed, SAI gases may be directed towards the turbine bypasspassage in order to expedite the heating of the second emission controldevice. After the second emission control device achieves operatingtemperature, the controller may decrease and/or discontinue SAI to oneor both of the exhaust manifold and the turbine bypass passage. In thisway, the performance of the exhaust system may be optimized through SAIvia the gas mixing tank reservoir.

FIG. 5 shows a graphical example of adjustments to engine operationbased on engine torque demand, as well as adjustments to the coolantflow to a gas mixing tank reservoir (e.g., such as the gas mixing tankreservoir 100 shown by FIG. 1, or the gas mixing tank reservoir 200shown by FIG. 2) based on the temperature of coolant delivered to thegas mixing tank reservoir. Specifically, graph 500 shows changes inengine torque demand at plot 502, changes in coolant flow to the gasmixing tank reservoir at plots 504, 506, and 508, changes in enginecoolant temperature at plot 512, changes in a coolant thresholdtemperature at plot 510, changes in secondary air injection (SAI) flowat plot 514, changes in low-pressure exhaust-gas recirculation (LP EGR)flow at plot 516, changes in high-pressure exhaust-gas recirculation (HPEGR) flow at plot 518, changes in flow from the gas mixing tankreservoir to the intake system to reduce compressor surge at plot 520,changes to the amount of gases in the gas mixing tank reservoir at plot522, and changes in the pressure of the gases in the gas mixing tankreservoir at plot 524. The coolant temperature sensor may be positionedat an inlet of the gas mixing tank reservoir and referred to herein asthe temperature sensor. The SAI, HP EGR, LP EGR, and intake air flow forcompressor surge may all be delivered by passages arranged between themixing tank reservoir and the intake and exhaust systems of the engine(and adjustments to valves disposed within those passage), such as thosedescribed above with reference to FIGS. 1 and 2. A controller (such ascontroller 169 shown in FIG. 1) may actuate actuators coupled to thevarious valves in order to adjust the SAI, LP EGR, HP EGR, and intakeair flow for compressor surge control to the engine intake and exhaustsystems from the gas mixing tank reservoir, as described further below.

Prior to time t1, engine torque demand is increasing (plot 502). Coolanttemperature (plot 510) of coolant flowing the gas mixing tank reservoiris also increasing. In one example, the increase in engine torque demandand coolant temperature may be due to an engine cold start (e.g., theengine adjusted from a non-operational state to an operational state).The amount of air (e.g., intake air and/or exhaust gases) in a gasmixing tank reservoir (plot 522) prior to time t1 remains approximatelyconstant. Additionally, the pressure of the air in the gas mixing tankreservoir (plot 524) prior to time t1 remains approximately constant. Inthis example, prior to time t1, intake air and/or exhaust had beenstored within the gas mixing tank reservoir during a prior operation ofthe engine (e.g., a substantial amount of time prior to time t1). Thestored air may then be utilized during a cold start, as described above.

At time t1, the controller (e.g., such as controller 169 shown byFIG. 1) receives a request for secondary air injection (SAI) to one orboth of an exhaust manifold or a turbine bypass passage. As describedduring the discussion of FIGS. 3A-3B and FIG. 4, the secondary airinjection request may be received in response to a measured temperatureof one or more emission control devices, and/or a measured rotationalspeed of a turbocharger turbine. In response to the request for SAI, thecontroller actuates one or more valves to increase the SAI flow rate(plot 514) to the exhaust manifold and/or turbine bypass passage. Sincecoolant temperature (plot 510) is below the threshold coolanttemperature (plot 512), coolant flow to the gas mixing tank reservoirremains turned off (e.g., does not flow to the reservoir) while SAI isdelivered between time t1 and time t2. During this time, coolanttemperature (plot 512) also increases.

In the time between t1 and t2, the engine coolant temperature has notyet reached a threshold value (plot 512). In response to the enginecoolant temperature being below the threshold value, the controller doesnot circulate coolant to the gas mixing tank reservoir. In this example,the threshold temperature between times t1 and t2 may be associated withthe temperature of the gases within the gas mixing tank reservoir aswell as the gases entering the reservoir through the intake system. Itmay be advantageous to inject gases at a higher temperature into theexhaust manifold to promote combustion of unburned fuel. In thissituation, the coolant temperature is relatively low and so coolant doesnot flow into the reservoir so that additional cooling of the gases isreduced.

The engine torque demand (plot 502) between time t1 and t2 remainsrelatively constant, and the engine is indicated to possess a relativelylow load. This may correspond to a warm-up phase of the engine, and/oror a cruising phase in which torque demand remains low. In this example,SAI may be requested to increase the temperature of one or more emissioncontrol devices to reduce engine emissions. As gases are initiallyrouted from the gas mixing tank reservoir to the exhaust manifold and/orturbine bypass passage between time t1 and time t2, the amount of air inthe reservoir decreases (plot 522) and the pressure in the reservoirdecreases (plot 524). However, the amount of air in the gas mixing tankreservoir reaches an approximately constant value as fresh air flowsinto the reservoir from the intake manifold in order to be injected intothe exhaust manifold. Similarly, the pressure in the reservoir arrivesat a relatively constant value due to the flow of intake air into thereservoir and out to the exhaust manifold.

Between time t2 and t3, engine torque demand (plot 502) increases again.As a result, coolant temperature (plot 510) also increases. Thethreshold temperature (plot 512) remains the same, as SAI flow is stillincreasing (plot 514). The amount of air in the reservoir (plot 522)begins to increase, and the pressure in the reservoir (plot 524) beginsto increase. In this example, the increased torque demand on the engineproduces an increased amount of exhaust gases, which in turn allow thecompressor of the turbocharger to spin more rapidly. More intake air isdelivered to the gas mixing tank reservoir, and while intake air is alsoexiting the reservoir and entering the exhaust system, a higher amountof gas is entering the reservoir than the gas that is leaving thereservoir.

The engine coolant temperature (plot 510) continues to increase and, attime t3, reaches the threshold temperature (plot 512). In response toreaching the threshold temperature, at time t3 the coolant is allowed toflow into the reservoir (as indicated by plot 504).

Between time t3 and t4, the engine torque demand (plot 502) remainsapproximately constant. The engine coolant temperature (plot 510)continues to increase past the threshold temperature (plot 512). Coolantflow to the reservoir (plot 504) increases in response to the continuedSAI flow (plot 514) combined with the increase in coolant temperaturebeyond the temperature threshold. The effect of flowing coolant to thereservoir in this example is to heat the gases within (and passingthrough) the reservoir. As described above, increasing the temperatureof the intake gas flowing through the reservoir may increase thecombustion reaction at the exhaust manifold. The amount of air in thereservoir continues to increase due to the reduction in SAI flow (plot514) and relatively constant engine torque demand (plot 502). In otherwords, the amount of gas exiting the reservoir decreases while theamount of gas entering the reservoir remains relatively constant. Thepressure of the gas in the reservoir (plot 524) also increases due tothe increase in temperature provided by the coolant as well as theincreased amount of gas stored within the volume of the reservoir (asdescribed above).

At time t4, the SAI flow (plot 514) stops. Between time t4 and t4, thecontroller determines that, due to rapidly increasing engine torquedemand (plot 502), HP EGR flow (plot 518) increases in accordance withthe torque demand. In response, the controller adjusts the temperaturethreshold value (plot 512) based on a temperature of the gases containedwithin the gas mixing tank reservoir and a temperature desired for HPEGR. In response to the temperature threshold change and the request toprovide HP EGR via the gas mixing tank reservoir, coolant flow to thegas mixing tank reservoir (plot 504) is stopped. For the currentexample, continuing to circulate coolant to the gas mixing tankreservoir would heat the gases within the reservoir. It is advantageousto keep the gases for HP EGR at a lower temperature (as described in thediscussion of FIGS. 3A-3B) and so coolant flow is stopped.

Due to the increased demand for HP EGR flow, the amount of air in thereservoir (plot 522) drops temporarily to fulfill the initial demand.The amount of air in the reservoir then stabilizes due to the increasedspeed of the turbine as the engine torque demand increases. Thestabilized amount of air in the reservoir corresponds to an equal inflowand outflow of gases from the gas reservoir. The increased exhaust flow(from the increased engine torque demand) and the increased intake flow(due to the increasing rotational speed of the compressor) allow anincreased flow into the gas mixing tank reservoir. As a result, thepressure within the reservoir (plot 524) increases until reaching astabilized point (consistent with an equal inflow and outflow of gasesas described above).

Between time t5 and t6, engine torque demand (plot 502) begins todecrease. As a result, coolant temperature (plot 510) also begins todecrease. The controller has determined that HP EGR flow is stilldesired and has adjusted the HP EGR flow (plot 518) according to thedecreasing engine torque demand. Due to the decreasing torque demand,the percentage of HP EGR gas delivered to the engine begins to decrease.The composition of HP EGR gas (e.g., the ratio of fresh intake air toexhaust gas) may be adjusted in accordance with the decreasing enginetorque demand to provide the desired amount of HP EGR injection. Theamount of gas in the reservoir (plot 522) decreases temporarily to keepup with HP EGR flow demand. Pressure within the reservoir (plot 524)remains approximately unchanged due to the introduction of higher EGRpercentage within the reservoir. The higher EGR percentage indicatesthat a greater amount of hot exhaust gas is stored within the mixingreservoir and so the pressure is higher when compared to a similar massof fresh intake air. The controller discharges the contents of thereservoir and allows in exhaust gas in a way that approximatelypreserves the pressure within the reservoir.

As the engine torque demand continues to decrease, the controllerpredicts the potential for compressor surge. In response to theprediction, the controller gradually decreases HP EGR flow until itstops at time t6. The controller also continues to charge the gas mixingtank reservoir with gas from the intake system and/or exhaust system inanticipation of potential compressor surge.

At time t6, the engine torque demand (plot 502) has decreased to a valueat which compressor surge may occur. In response to the indication ofpotential surge, the controller determines that air from the gas mixingtank reservoir be discharged to the inlet of the compressor (plot 520)in order to reduce surging of the compressor. In response to thedetermination to reduce surge, the controller adjusts the thresholdcoolant temperature (plot 512) to a lower value based on the temperatureof the gases in the reservoir. The engine coolant temperature (plot 510)at time t6 is higher than the new coolant threshold temperature, and inresponse, coolant begins flowing through the gas mixing tank reservoir(plot 506). In this example, the controller determines that it isadvantageous to circulate coolant in order to heat the gases within thegas mixing tank reservoir. Heating the gases increases the pressurewithin the tank, and the gases at increased pressure can be dischargedinto the compressor inlet to reduce surge.

The sudden discharging of gases into the compressor inlet (plot 520)decreases the amount of gas stored in the reservoir (522). The reducedamount of gas in the reservoir then reduces the pressure of the gases inthe reservoir (plot 524). The engine torque demand (plot 502) thenbegins to increase again between time t6 and t7. As the engine torquedemand increases, of the potential for compressor surge decreases and sothe controller reduces the flow of gases from the reservoir to thecompressor inlet until the flow stops at t7. The amount of air and thepressure of the air within the reservoir begins to increase until t7.

Between times t7 and t8, the engine torque demand (plot 502) remainsapproximately constant with little fluctuation. The controllerdetermines at time t7 that LP EGR flow is desired based on additionalengine operating conditions. At time t7, the controller beginsincreasing the flow of LP EGR gases (plot 516) to the engine from thegas mixing tank reservoir. In response to the flow of LP EGR, thecontroller adjusts the coolant temperature threshold (512) to a highervalue based on the temperature of the gases within the gas mixing tankreservoir. However, between t7 and t8 the temperature of the enginecoolant (plot 510) is still above the threshold value and so coolantdoes not flow through the gas mixing tank reservoir. It is advantageousto flow LP EGR gases at lower temperatures (as described in thediscussion of FIGS. 3A-3B above) and so flowing coolant through thereservoir between time t7 and t8 would provide the disadvantageouseffect of increasing the temperature of the gases.

The steady engine torque demand results in a charging opportunity forthe gas mixing tank reservoir. As a result, the amount of air in thereservoir (plot 522) begins to increase. The ratio of the exhaust air tothe intake air is varied by the controller to maintain a constantpressure (plot 524) within the reservoir.

After time t8, the temperature of the engine coolant (plot 510)decreases below the threshold coolant temperature (plot 512). Inresponse to the decreased coolant temperature in combination with thecontinued demand for LP EGR, the controller begins flowing coolant intothe gas mixing tank reservoir (plot 508). The flow of coolant cools thegases within the reservoir, and the controller adjusts the percentage ofEGR gas within the reservoir to maintain a constant pressure (plot 524)within the reservoir. The inflow and outflow of gases from the reservoirstabilizes such that a constant amount of gas is contained within thereservoir after time t8 (plot 522). Additionally, the flow of LP EGRreaches a constant value (plot 516) in accordance with engine torquedemand (plot 502).

In this way, the controller within the engine system may regulate theflow of gases to the gas mixing tank reservoir from the intake systemand/or the exhaust system based on engine operating conditions. Thecontroller may also regulate the flow of gases from the gas mixing tankreservoir to one or more locations within the intake system and one ormore locations within the exhaust system based on engine operatingconditions. The flow of gases to/from the gas mixing tank reservoir maybe influenced at least in part by the temperature of the engine coolant.The controller may determine a threshold coolant temperature for eachprocess occurring (e.g., LP EGR flow, SAI, etc.) and regulate the flowof coolant to the gas mixing tank reservoir based on a comparison of theengine coolant temperature with the coolant threshold temperature.Coolant flow to the gas mixing tank reservoir is adjusted by thecontroller based on coolant temperature. Coolant flow to the gas mixingtank reservoir is also adjusted based on one or more requests to atleast partly discharge the gases contained within the gas mixing tankreservoir to provide the engine system with secondary air injection(SAD, low-pressure exhaust gas recirculation (LP EGR), high-pressureexhaust gas recirculation (HP EGR), and/or compressor surge control. Thetechnical effect of adjusting coolant flow to the gas mixing tankreservoir based on one or more requests for SAI, LP EGR, HP EGR, and/orcompressor surge control is to control the temperature of the gasesdischarged from the gas mixing tank reservoir to the intake/exhaustsystem. In one example, the discharge of gases from the gas mixing tankreservoir may be delayed until the gas temperature within the reservoirreaches a desired temperature, and where the desired temperature isbased on the location of discharge (e.g., to one or more locationswithin the intake system and/or exhaust system). In this way, thetemperature of SAI, LP EGR, HP EGR, and compressor surge control gasescan be controlled to increase engine efficiency. By regulating the flowsof gases to/from the gas mixing tank reservoir and coolant to/from thegas mixing tank reservoir, engine performance may be increased.

FIGS. 6-9 present additional embodiments of a heat exchanger with mayinclude similar features to the mixing tank reservoir (e.g., heatexchanger) presented above in the discussion of FIGS. 1-2. However, theembodiments of the heat exchanger (and the corresponding controls)presented in FIGS. 6-12 include a heat exchanger with an integratedenergy recovery device, where the energy recovery device is physicallyand fluidly coupled with the heat exchanger. Specifically, FIG. 6 andFIG. 8 show additional schematics of example engine systems including aheat exchanger which may include similar features to the mixing tankreservoir of FIG. 1. Engine system 600 shown by FIG. 6 and engine system800 shown by FIG. 8 include several components similar to those shown byengine system 166 of FIG. 1 and have been numbered similarly. Componentsshown by FIG. 6 and FIG. 8 that are included within engine system 166 ofFIG. 1 and introduced during the discussion of FIG. 1 above may not bere-introduced in the following discussions of FIG. 6 and FIG. 8 below.Similarly, FIG. 7 and FIG. 9 show additional embodiments of the heatexchanger (e.g., heat exchanger 700 in FIG. 7 and heat exchanger 900 inFIG. 9), where heat exchanger 700 may be used as the heat exchanger 601shown in FIG. 6 and heat exchanger 900 may be used as the heat exchanger801 in FIG. 8. Turning first to FIG. 6, engine system 600 includesengine 168, cylinder head 182, combustion chambers (such as combustionchamber 180), and fuel injectors (such as fuel injector 179). Enginesystem 600 also includes turbocharger 174 comprised of shaft 171,compressor 184, and turbine 186. Compressor 184 of turbocharger 174 isarranged within an intake system 670, while turbine 186 of turbocharger174 is arranged within an exhaust system 672. The turbine 186 andcompressor 184 are coupled by shaft 171, as described during thediscussion of FIG. 1. The intake system 670 includes several componentssimilar to those shown by FIG. 1, such as intake passage 181, aircleaner 183, charge-air cooler 185, throttle 187, intake manifold 176,and pressure sensor 175. Similarly, the exhaust system 672 includesseveral components similar to those shown by FIG. 1, such as exhaustmanifold 178, pressure sensor 177, first emissions control device 188,temperature sensor 189, second emissions control device 190, temperaturesensor 195, temperature sensor 191, flow sensor 192, and exhaust conduit193.

Engine system 600 also includes heat exchanger 601 coupled to bothintake system 670 and exhaust system 672. Heat exchanger 601 isconfigured to both receive and output air from the intake system 670,and to both receive and output exhaust gas from the exhaust system 672,as described in further detail below and by the discussion of FIG. 7presented below.

Heat exchanger 601 includes energy recovery device 604 which iselectrically coupled to battery 602. In one example, the energy recoverydevice 604 is integrated with the heat exchanger 601 such that theenergy recovery device 604 is fluidly and physically coupled (e.g.,directly coupled without any intervening components separating theenergy recovery device 604 and the heat exchanger 601) to the heatexchanger 601. As explained further below, passages of the energyrecovery device configured to flow exhaust gas may be directly coupledto passages of the heat exchanger configured to flow exhaust gas.

Energy recovery device 604 may be a thermoelectric generator (such as aSeebeck generator, Peltier device, etc.) configured to convert heat intoelectrical energy. For example, a first side (not shown) of the energyrecovery device 604 may be held at approximately a first temperaturethrough a thermal coupling with a first temperature reservoir. Thethermal coupling between the first side of the energy recovery deviceand the first temperature reservoir may include components such as heatsinks, fans, coolant circulation, etc. in direct contact with the firsttemperature reservoir to transfer thermal energy away from the firstside and into the reservoir. The first temperature reservoir maycomprise a fluid and/or surface at a temperature lower than atemperature of engine exhaust gases (e.g., ambient air) and may have arelatively high specific heat and/or volume such that the transfer ofthermal energy from the first side of the energy recovery device to thefirst reservoir does not appreciably adjust the temperature of the firsttemperature reservoir. A second side of the energy recovery device isthermally coupled with engine exhaust gases such that the second side ofthe energy recovery device may receive thermal energy and be heated bythe exhaust gases. The thermal coupling between the second side of theenergy recovery device and the exhaust gases may include components suchas heat sinks, fans, fluid circulation, etc. in direct contact with theexhaust gases to transfer thermal energy away from the exhaust gases andinto the second side of the energy recovery device.

Battery 602 may be configured to store electrical energy generated byenergy recovery device 604 and supply electrical energy to engine system600. For example, battery 602 may store electrical energy duringconditions of engine operation such as those described in the discussionof FIGS. 11-12 below. In one example, battery 602 may store electricalenergy from energy recovery device 604 during periods of high engineload. Stored electrical energy from battery 602 may then be supplied tothe engine system 600 in response to a request from a controller, suchas controller 669 of control system 667. In one example, storedelectrical energy within battery 602 may be utilized during an enginecold start and/or to supply power to one or more electrical components603 of engine system 600. Example electrical components (such aselectrical component 603) may include accessory devices of engine system600 (such as lights of a vehicle passenger compartment), a controller(such as controller 669), one or more fluid pumps, heaters, compressors,etc. The electrical component 603 shown by FIG. 6 is not limited to theexample electrical components mentioned above. Engine system 600 mayalso include additional electrical components (e.g., in addition toelectrical component 603 and not shown) electrically coupled to battery602.

The controller 669 may comprise a similar structure and configuration asthat of controller 169 described above in the discussion of FIG. 1.However, the controller 669 includes instructions and logic specific tooperation of engine system 600. In particular, controller 669 isconfigured with instructions stored in non-transitory memory foroperation of heat exchanger 601, energy recovery device 604, andactuators 663 associated with valves (e.g., such as four-way valve 650,four-way valve 633, three-way valve 630, valve 610, valve 646, etc.) andsensors 665 within engine system 600.

Intake system 670 and exhaust system 672 of engine system 600 eachinclude a plurality of passages coupled to heat exchanger 601 to flowgases to the heat exchanger 601. Intake air passage 608 is arrangedupstream of charge-air cooler 185 and downstream of compressor 184 tosupply compressed intake air to an intake port 612 of heat exchanger601. A valve 610 is included within intake air passage 608 and may beactuated by controller 669 to increase or decrease the flow of intakeair into the heat exchanger 601. Check valve 611 is coupled to intakeair passage 608 to reduce the likelihood of pressurized intake airflowing from the intake port 612 of the heat exchanger 601 back throughintake air passage 608.

A first exhaust passage 616 is coupled to the exhaust system 672upstream of first emissions control device 188 and supplies exhaust gasfrom the exhaust system 672 to a first exhaust port 620 of the heatexchanger 601. A valve 618 is included within first exhaust passage 616and may be actuated by controller 669 to increase or decrease the flowof exhaust gas into the heat exchanger 601 through first exhaust passage616. Check valve 619 is coupled to first exhaust passage 616 to reducethe likelihood of exhaust gas flowing from the first exhaust port 620 ofthe heat exchanger 601 back through first exhaust passage 616.

Four-way valve 633 is arranged downstream of first emissions controldevice 188 and upstream of turbine 186 within the exhaust system 672.Four-way valve 633 is coupled to the exhaust conduit 193 and may beactuated (e.g., opened or closed or moved into a plurality of positionsbetween fully opened and fully closed) to increase or decrease the flowof exhaust gases through exhaust conduit 193. Four-way valve 633 isadditionally coupled to a second exhaust passage 615 and a turbinebypass passage 635. Exhaust gas may flow from the exhaust system 672through second exhaust passage 615 gas to a second exhaust port 623 ofthe heat exchanger 601 when four-way valve 633 is actuated (e.g., openedor closed) by controller 669 according to the examples described below.Actuation of four-way valve 633 may increase or decrease the flow ofexhaust gas from exhaust conduit 193 to second exhaust passage 615.Check valve 621 is coupled to second exhaust passage 615 to reduce thelikelihood of exhaust gas flowing from the second exhaust port 623 ofthe heat exchanger 601 back through second exhaust passage 615.

The four-way valve 633 may be normally closed to the second exhaustpassage 615 and the turbine bypass passage 635 so that gases do not flowinto the second exhaust passage 615 and the turbine bypass passage 635via exhaust conduit 193. However, the four-way valve 633 may be actuated(e.g., opened) by the controller 669 to allow gases to flow through thefour-way valve 633 from the exhaust conduit into one or more of thesecond exhaust passage 615 and the turbine bypass passage 635.

In a first example, the four-way valve 633 may be opened to both thesecond exhaust passage 615 and a first portion 637 of exhaust conduit193 to increase the flow of gases from the exhaust conduit 193 into thesecond exhaust passage 615, but closed to the turbine bypass passage 635to reduce the flow of gases through turbine bypass passage 635, closedto a second portion 639 of exhaust conduit 193 to reduce the flow ofgases towards turbine 186, or closed to both of the turbine bypasspassage 635 and the second portion 639 of exhaust conduit 193 to reducethe flow of gases towards both the turbine 186 and the turbine bypasspassage 635. In this way, the four-way valve 633 arranged downstream offirst emissions control device 188 increases the flow of exhaust gasesinto the heat exchanger 601 from the exhaust manifold 178 via the secondexhaust passage 615 coupled to exhaust conduit 193. In a second example,the four-way valve 633 may be opened to both the turbine bypass passage635 and the first portion 637 of exhaust conduit 193 to increase theflow of exhaust gases from the exhaust conduit 193 into the turbinebypass passage 635, and closed to the second exhaust passage 615 toreduce the flow of gases towards second exhaust passage 615, closed tothe second portion 639 of exhaust conduit 193 to reduce the flow ofgases towards turbine 186, or closed to both of the second exhaustpassage 615 and the second portion 639 of exhaust conduit 193 to reducethe flow of gases towards both the second exhaust passage 615 and theturbine 186. In this way, the four-way valve 633 may decrease the flowof exhaust gas through turbine 186, and decrease the flow of exhaustthrough second exhaust passage 615 towards heat exchanger 601. In athird example, the four-way valve 633 may be opened to the first portion637 of exhaust conduit 193, opened to the second exhaust passage 615,and opened to the turbine bypass passage 635 to increase the flow ofgases from the exhaust conduit 193 into each of the second exhaustpassage 615 and the turbine bypass passage 635, and closed to the secondportion 639 of exhaust conduit 193 to reduce the flow of gases throughexhaust conduit 193 towards turbine 186. In this way, a first portion ofthe gas flow through exhaust conduit 193 is directed towards heatexchanger 601 via second exhaust passage 615 while a second portion ofthe gas flow is directed past the turbine 186 through turbine bypasspassage 635. In a fourth example, the four-way valve 633 may be openedto both the first portion 637 of exhaust conduit 193 and the secondportion 639 of exhaust conduit 193 to increase the flow of gases fromthe exhaust manifold 178 through the exhaust conduit 193 towards theturbine 186, but closed to the turbine bypass passage 635 to reduce theflow of gases towards turbine bypass passage 635, closed to the secondexhaust passage 615 to reduce the flow of gases towards the secondexhaust passage 615, or closed to both the turbine bypass passage 635and the second exhaust passage 615 to reduce the flow of gases towardsboth of the turbine bypass passage 635 and the second exhaust passage615. In this way, four-way valve 633 may increase the flow of exhaustgas through turbine 186 (e.g., in order to increase a speed of turbine186). In a fifth example, the four-way valve 633 may be opened or closedto each of the first portion 637 of exhaust conduit 193, the secondportion 639 of exhaust conduit 193, the turbine bypass passage 635, andthe second exhaust passage 615 to increase or decrease the flow ofexhaust gas towards each of the turbine 186, the turbine bypass passage635, and the second exhaust passage 615.

By actuating the four-way valve 633 according to the examples describedabove, the heat exchanger 601 may receive exhaust gases from the exhaustconduit 193 downstream of the first emissions control device 188 (e.g.,during conditions in which increasing a temperature of the firstemissions control device 188 via exhaust flow is desired, such as duringan engine cold start). Additionally, the flow of gases in exhaustconduit 193 may be selectively diverted past the turbine 186 via turbinebypass passage 635 to reduce an operating speed of the turbine 186(e.g., to reduce the likelihood of compressor choke from occurring, suchas during periods of high engine load). Actuation of the four-way valve633 may include fully opening or closing the valve to increase ordecrease flow from one or more of the coupled passages from travelingthrough the four-way valve 633. Actuation may also include increasing ordecreasing an amount of opening of the four-way valve 633 to a positionbetween fully open and fully closed in order to increase or decreaseflow from one or more of the coupled passages from traveling through thefour-way valve 633.

Heat exchanger 601 is additionally coupled to a plurality of passages ofeach of the intake system 670 and exhaust system 672 to flow gas out ofthe heat exchanger 601. A first return passage 629 (e.g., similar to thesecond external split passage 129 shown by FIG. 1 and described above inthe discussion of FIG. 1) is coupled to a first return port 628 of theheat exchanger 601 and directs the flow of compressed air out of heatexchanger 601. The flow of compressed air from heat exchanger 601through first return passage 629 is controlled by actuation of three-wayvalve 630 (e.g., similar to three-way valve 130 shown by FIG. 1 anddescribed above in the discussion of FIG. 1). The three-way valve 630 isadditionally coupled to a first secondary air injection (SAI) passage632 (e.g., such as the first SAI passage 132 shown by FIG. 1 anddescribed above in the discussion of FIG. 1) and a second secondary airinjection (SAI) passage 631 (e.g., such as the second SAI passage 131shown by FIG. 1 and described above in the discussion of FIG. 1). Thesecond SAI passage 631 is coupled to the turbine bypass passage 635.

Three-way valve 630 is actuated (e.g., opened or closed) by controller669 in a variety of ways described during the discussion of theactuation of three-way valve 130 of FIG. 1. For example, three-way valve630 may be opened to both of the first return passage 629 and the firstSAI passage 632 to increase a flow of compressed air from the heatexchanger 601 through the first return passage 629 to the first SAIpassage 632, and closed to the second SAI passage 631 to decrease a flowof compressed air from the heat exchanger 601 to the second SAI passage631. Alternately, the three-way valve 630 may be opened to both of thefirst return passage 629 and the second SAI passage 631 to increase theflow of compressed air from the heat exchanger 601 to the second SAIpassage 631 via first return passage 629, and closed to the first SAIpassage 632 to decrease the flow of compressed air from the heatexchanger 601 to the first SAI passage 632. As an additional example,the three-way valve 630 may be opened to the first return passage 629 toincrease a flow of compressed air from the heat exchanger 601 throughthe first return passage 629, and opened or closed to both of the firstSAI passage 632 and the second SAI passage 631 to increase or decrease aflow of compressed air from the first return passage 629 to both of thefirst SAI passage 632 and the second SAI passage 631.

Heat exchanger 601 is additionally coupled to a second return passage648 via second return port 613 and a third return passage 649 via thirdreturn port 644. The second return passage 648 is coupled to intakepassage 181 of intake system 670 downstream of air cleaner 183 andupstream of compressor 184. Flow of compressed air from heat exchanger601 through second return passage 648 is adjusted by actuation of valve646. Valve 646 may be actuated (e.g., opened or closed) by thecontroller 669 to increase or decrease a flow of compressed air out ofheat exchanger 601 and into the intake passage 181. As an example, valve646 may be opened to increase the flow of compressed air towards thecompressor 184 in order to reduce the likelihood of compressor surgefrom occurring.

The third return passage 649 is coupled between third return port 644and four-way valve 650. Exhaust gas flow from the third return port 644of the heat exchanger 601 through the third return passage 649 may beadjusted when the four-way valve 650 is actuated (e.g., opened orclosed) by controller 669 according to the examples described below.Actuation of four-way valve 650 may increase or decrease the flow ofexhaust gas from the heat exchanger 601 to the third return passage 649.

The four-way valve 650 may be normally closed to the third returnpassage 649 so that gases do not flow from the heat exchanger 601 intothe third return passage 649. However, the four-way valve 650 may beactuated by the controller 669 to allow gases to flow through thefour-way valve 650 from the heat exchanger into one or more of aplurality of passages coupled to the four-way valve 650, such an exhaustreturn line 651, a high-pressure (HP) EGR passage 607, or a low-pressure(LP) EGR passage 652.

In a first example of actuation of the four-way valve 650, the four-wayvalve 650 may be opened to both of the third return passage 649 and theHP EGR passage 607 to increase a flow of gases through the third returnpassage 649 toward the HP EGR passage 607, but closed to both of the LPEGR passage 652 and the exhaust return line 651 to reduce a flow ofgases from the third return passage 649 towards the LP EGR passage 652and the exhaust return line 651. In this way, the four-way valve 650increases the injection of exhaust gas into the intake system 670 at alocation downstream of the compressor 184 to adjust an amount of HP EGRprovided to the engine system 600. In a second example of actuation ofthe four-way valve 650, the four-way valve 650 may be opened to both ofthe third return passage 649 and the exhaust return line 651 to increasea flow of gases through the third return passage 649 toward the exhaustreturn line 651, but closed to both of the LP EGR passage 652 and the HPEGR passage 607 to reduce a flow of gases from the third return passage649 towards the LP EGR passage 652 and the HP EGR passage 607. In thisway, the four-way valve 650 decreases an injection of exhaust gas intothe intake system 670 and increases an injection of exhaust gas backinto the exhaust system 672. In a third example of actuation of thefour-way valve 650, the four-way valve 650 may be opened to both of thethird return passage 649 and the LP EGR passage 652 to increase a flowof gases through the third return passage 649 toward the LP EGR passage652, but closed to both of the HP EGR passage 607 and the exhaust returnline 651 to reduce a flow of gases from the third return passage 649towards the HP EGR passage 607 and the exhaust return line 651. In thisway, the four-way valve 650 increases the injection of exhaust gas intothe intake system 670 at a location upstream of the compressor 184 toadjust an amount of LP EGR provided to the engine system 600. In afourth example of actuation of the four-way valve 650, the four-wayvalve 650 may be opened to each of the third return passage 649, the HPEGR passage 607, and the LP EGR passage 652 to increase a flow of gasesthrough the third return passage 649 toward each of the HP EGR passage607 and the LP EGR passage 652, but closed to exhaust return line 651 toreduce a flow of gases from the third return passage 649 towards theexhaust return line 651. In this way, the four-way valve 650 increasesthe injection of exhaust gas into the intake system 670 both upstreamand downstream of the compressor 184 to adjust an amount of LP EGR andHP EGR provided to the engine system 600. In a fifth example ofactuation of the four-way valve 650, the four-way valve 650 may beopened to each of the third return passage 649, the LP EGR passage 652,and the exhaust return line 651 to increase a flow of gases through thethird return passage 649 toward each of the LP EGR passage 652 and theexhaust return line 651, but closed to HP EGR passage 607 to reduce aflow of gases from the third return passage 649 towards the HP EGRpassage 607. In this way, the four-way valve 650 increases the injectionof exhaust gas into the intake system 670 upstream of the compressor 184to adjust the amount of LP EGR provided to the engine system 600, andincreases the injection of exhaust gas back into the exhaust system 672via exhaust return line 651. In a sixth example of actuation of thefour-way valve 650, the four-way valve 650 may be opened to each of thethird return passage 649, the HP EGR passage 607, and the exhaust returnline 651 to increase a flow of gases through the third return passage649 toward each of the HP EGR passage 607 and the exhaust return line651, but closed to LP EGR passage 652 to reduce a flow of gases from thethird return passage 649 towards the LP EGR passage 652. In this way,the four-way valve 650 increases the injection of exhaust gas into theintake system 670 downstream of the compressor 184 to adjust the amountof HP EGR provided to the engine system 600, and increases the injectionof exhaust gas back into the exhaust system 672 via exhaust return line651. In a seventh example of actuation of the four-way valve 650, thefour-way valve 650 may be opened to each of the third return passage649, the HP EGR passage 607, the LP EGR passage 652, and the exhaustreturn line 651 to increase a flow of gases through the third returnpassage 649 toward each of the HP EGR passage 607, LP EGR passage 652,and exhaust return line 651. In this way, the four-way valve 650increases the injection of exhaust gas into the intake system 670 bothupstream and downstream of the compressor 184 to adjust an amount of LPEGR and HP EGR provided to the engine system 600, and increases theinjection of exhaust gas back into the exhaust system 672 via exhaustreturn line 651.

By actuating the four-way valve 650 with the controller 669 according tothe examples described above, the heat exchanger 601 may flow exhaustgases to provide HP EGR and/or LP EGR based on engine operationconditions (e.g., during conditions in which reduced NOx emissions aredesired and engine load is sufficiently high). Additionally, the flow ofgases from heat exchanger 601 may be selectively diverted back to theexhaust system 672 via exhaust return line 651 to reduce an amount ofEGR gases supplied to engine system 600 (e.g., during conditions inwhich a higher percentage of fresh intake air is desired, such as athrottle tip-in). Actuation of the four-way valve 650 may include fullyopening or closing the valve to increase or decrease flow from one ormore of the coupled passages from traveling through the four-way valve650. Actuation may also include increasing or decreasing an amount ofopening of the four-way valve 650 to a position between fully open andfully closed in order to increase or decrease flow from one or more ofthe coupled passages from traveling through the four-way valve 650.

By configuring the engine system 600 in this way, the heat exchanger 601may receive exhaust gas from the exhaust system 672 and intake air fromthe intake system 670. The heat exchanger 601 may convert thermal energyof exhaust gas into electrical energy via energy recovery device 604disposed within the heat exchanger 601 and coupled to battery 602. Theheat exchanger 601 may then return intake air and/or exhaust gas to oneor each of the intake system 670 or the exhaust system 672 to supplyEGR, SAI, and/or compressor surge reduction. In this way, engineperformance may be increased.

FIG. 7 shows an embodiment of a heat exchanger, such as the heatexchanger 601 shown in FIG. 6. The heat exchanger 700 shown by FIG. 7includes an energy recovery device (such as the energy recovery device604 shown by FIG. 6 and described above in the discussion of FIG. 6), afirst plurality of passages 703 coupled between an inlet intake airmanifold 705 and an outlet intake air manifold 708 internal to a housing702 of the heat exchanger 700, and a second plurality of passages 709coupled between an inlet exhaust manifold 706 and an outlet exhaustmanifold 707 internal to the housing 702 of the heat exchanger 700. Thefirst plurality of passages 703 and the second plurality of passages 709of the heat exchanger 700 are configured proximate to each other withinan internal volume of the heat exchanger 700 to facilitate a transfer ofthermal energy from exhaust gases flowing through the second pluralityof passages 709 to intake air flowing through the first plurality ofpassages 703. As an example, the second plurality of passages 709 may bearranged approximately perpendicular to the first plurality of passages703 within the housing 702 of the heat exchanger 700 to increase aninterface area between the second plurality of passages 709 and thefirst plurality of passages 703. The interface area between the firstplurality of passages 703 and the second plurality of passages 709 mayinclude a thermally conductive material (e.g., metal) to facilitate thetransfer of thermal energy from exhaust gases flowing through the secondplurality of passages 709 to the intake air flowing through the firstplurality of passages 703 while retaining fluidic isolation of theexhaust gas from the intake air. In other words, gases within the secondplurality of passages 709 may exchange thermal energy with the intakeair within the first plurality of passages 703, but the first pluralityof passages 703 and the second plurality of passages 709 do not exchangeand/or mix gases with each other.

Included with and/or coupled to the housing 702 of the heat exchanger700 are a plurality of inlet and outlet ports functionally similar tothe ports of the heat exchanger 601 shown by FIG. 6. The embodiment ofthe heat exchanger shown by FIG. 7 includes a first exhaust inlet port720, a second exhaust inlet port 714, an intake air inlet port 738, anintake air outlet port 742, and an exhaust outlet port 764. Alternateembodiments may contain a different number of ports. For example, in oneembodiment (not shown), the first exhaust inlet port 720 and the secondexhaust inlet port 714 may be combined into a single exhaust inlet portreceiving exhaust gas flow from a plurality of passages.

The ports facilitate the flow of gases to and from the heat exchanger700. The first exhaust inlet port 720 is coupled to a first exhaustinlet passage 716, such as the first exhaust passage 616 shown by FIG. 6and described during the discussion of FIG. 6 above. The first exhaustinlet passage 716 is coupled to a location upstream of a first emissioncontrol device of an exhaust system, such as the first emission controldevice 188 of exhaust system 672 shown by FIG. 6, and flows exhaust gasto the heat exchanger in a direction indicated by arrow 718. The secondexhaust inlet port 714 is coupled to a second exhaust inlet passage 710,such as the second exhaust passage 615 shown by FIG. 6 and describedduring the discussion of FIG. 6 above. The second exhaust inlet passage710 is coupled to a location downstream of the first emission controldevice of the exhaust system, and flows exhaust gas to the heatexchanger 700 in a direction indicated by arrow 712.

The intake air inlet port 738 is coupled to an intake air passage 734,such as the intake air passage 608 shown by FIG. 6 and described duringthe discussion of FIG. 6 above. The intake air passage 734 is coupled toan intake system downstream of a compressor, such as the compressor 184of the intake system 670 shown by FIG. 6. The intake air passage 734flows compressed intake air from the intake system to the heat exchanger700 in a direction indicated by arrow 736.

Compressed intake air flows through intake air inlet port 738 into theinlet intake air manifold 705 (internal to the interior of the heatexchanger 700) towards the first plurality of passages 703 (which mayherein be referred to as exchanger intake passages 703). The intake airflows through the exchanger intake passages 703 towards the outletintake air manifold 708 and is directed to intake air outlet port 742.

The intake air outlet port 742 is coupled to a first intake air outletpassage 744. Intake air flows out of the intake air outlet port 742through the first intake air outlet passage 744 in a direction indicatedby arrow 746. The first intake air outlet passage 744 is coupled to asecond intake air outlet passage 750 via a first valve 748. The secondintake air outlet passage 750 (e.g., similar to second return passage648 shown by FIG. 6) selectively flows gases from the heat exchanger 700to a location upstream of the compressor in the intake system viaactuation of valve 748 by a controller (such as controller 669 shown byFIG. 6). For example, a flow of gas through the second intake air outletpassage 750 from the heat exchanger 700 in a direction indicated byarrow 752 may be increased or decreased by actuation of the valve 748.

The first intake air outlet passage 744 is additionally coupled to afirst secondary air injection passage 753 and a second secondary airinjection passage 756 via a single valve 754 (e.g., a three-way valve754). The first secondary air injection passage 753 (e.g., such as firstSAI passage 632 shown by FIG. 6) selectively flows gases from the heatexchanger 700 in a direction indicated by arrow 755 to a locationupstream of the first emissions control device (such as the firstemissions control device 188 shown by FIG. 6) of the exhaust system(such as the exhaust system 672 shown by FIG. 6) via actuation ofthree-way valve 754. Three-way valve 754 may open or close via thecontroller in a plurality of ways similar to the actuation of three-wayvalve 630 described above in the discussion of FIG. 6. For example, thecontroller may open or close the three-way valve 754 to the first SAIpassage 753 to increase or decrease the flow of gases from first intakeair outlet passage 744 into first SAI passage 753. The second secondaryair injection passage 756 selectively flows gases from the heatexchanger 700 in a direction indicated by arrow 758 to a locationdownstream of the first emissions control device and downstream of aturbine (such as turbine 186 shown by FIG. 6) via actuation of three-wayvalve 754. For example, the controller may open or close the three-wayvalve 754 to the second SAI passage 756 to increase or decrease the flowof gases from first intake air outlet passage 744 into second SAIpassage 756. In this way, the flow of gas from the heat exchanger 700through first SAI passage 753 may be adjusted by opening or closing thethree-way valve 754 to the first SAI passage 753, the flow of gas fromthe heat exchanger 700 through the second SAI passage 756 may beadjusted by opening or closing the three-way valve 754 to the second SAIpassage 756, and the flow through both of the first SAI passage 753 andthe second SAI passage 756 may be adjusted by opening or closing thethree-way valve to each of the first SAI passage 753 and the second SAIpassage 756. The flow of gas to both of the first SAI passage 753 andthe second SAI passage 756 may additionally be adjusted by opening orclosing (via the controller) three-way valve 754 to the first intake airoutlet passage 744, and not opening or not closing the three-way valve754 to either of the first SAI passage 753 or the second SAI passage756.

In a first example of actuation of three-way valve 754, the three-wayvalve 754 may be opened to the first SAI passage 753 by the controllerto increase the flow of gases from the heat exchanger 700 to the firstSAI passage 753, and closed to the second SAI passage 756 by thecontroller to decrease the flow of gases from the heat exchanger 700 tothe second SAI passage 756. By increasing the flow of gases to the firstSAI passage 753, the first emissions control device may achieve anincreased temperature at an increased rate due to an exothermic reactionbetween the injected gases and unburnt fuel in the exhaust system. In asecond example of actuation of valve 754, the three-way valve 754 may beclosed to the first SAI passage 753 by the controller to decrease theflow of gases from the heat exchanger 700 to the first SAI passage 753,and opened to the second SAI passage 756 by the controller to increasethe flow of gases from the heat exchanger 700 to the second SAI passage756. By increasing the flow of gases to the second SAI passage 756, asecond emissions control device (e.g., such as the second emissionscontrol device 190 shown by FIG. 6) downstream of the first emissionscontrol device may achieve an increased temperature at an increased ratedue to exothermic reaction between the injected gases and unburnt fuelin the exhaust system. In a third example of actuation of valve 754, thethree-way valve 754 may be opened or closed to both the first SAIpassage 753 and the second SAI passage 756 by the controller to increaseor decrease the flow of gases from the heat exchanger 700 to both thefirst SAI passage 753 and the second SAI passage 756. By adjusting(e.g., increasing or decreasing) the flow to both the first SAI passage753 and the second SAI passage 756 from the heat exchanger 700, a totalflow of gases from the intake system to the exhaust system may beincreased or decreased to increase engine performance.

Exhaust gases from the exhaust system flow through the first exhaustinlet passage 716 coupled to the first exhaust inlet port 720 and intothe heat exchanger 700. Flow of gases through first exhaust inletpassage 716 may be increased or decreased by the controller viaactuation of a first valve (e.g., such as valve 618 shown by FIG. 6).Exhaust gases from the exhaust system also flow through the secondexhaust inlet passage 710 coupled to the second exhaust inlet port 714and into the heat exchanger 700. Flow of gases through second exhaustinlet passage 710 may be increased or decreased by the controller viaactuation of a second valve (e.g., such as the four-way valve 633 shownby FIG. 6).

First exhaust inlet passage 716 flows gases from a location upstream ofthe first emissions control device to the heat exchanger 700 whilesecond exhaust inlet passage 710 flows gases from a location downstreamof the first emissions control device to the heat exchanger 700 (asdescribed above). The gases flowing through the second exhaust inletpassage 710 may be at a lower temperature than the gases flowing throughthe first exhaust inlet passage 716 due to an interaction of the exhaustgases with the first emissions control device. For example, the firstemissions control device may receive a portion of the thermal energy ofthe exhaust gas before the exhaust gas flows through the second exhaustinlet passage 710. By actuating the first valve and/or the second valvevia the controller to adjust the flow of exhaust gases into the heatexchanger via the first exhaust inlet passage 716 and the second exhaustinlet passage 710, a temperature of the exhaust gases entering the heatexchanger 700 may be selectively adjusted.

Exhaust gases entering the first exhaust inlet port 720 flow through afirst exhaust passage 724 internal to an interior of the heat exchanger700, and exhaust gases entering the second exhaust inlet port 714 flowthrough a second exhaust passage 722 internal to the interior of theheat exchanger 700. The first exhaust passage 724 and the second exhaustpassage 722 are both fluidically coupled to the energy recovery device704 arranged internal to the interior of the heat exchanger 700. Theembodiment of the heat exchanger 700 shown by FIG. 7 includes the energyrecovery device 704 entirely within the interior of the heat exchanger700. However, alternate embodiments (not shown) may include one or moresurfaces of the energy recovery device arranged external to the interiorof the heat exchanger.

The energy recovery device 704 is a device (such as a Peltier device, asdescribed above in the discussion of FIG. 6) that utilizes heat fromexhaust gases to generate electrical energy. For example, exhaust gasesmay flow from one or both of the first exhaust inlet port 720 or thesecond exhaust inlet port 714 into an inlet port 726 of the energyrecovery device 704 via the first exhaust passage 724 or the secondexhaust passage 722 respectively. Exhaust gases flowing through theinlet port 726 of the energy recovery device 704 may transfer thermalenergy to an electrically conductive element 784 of the energy recoverydevice 704. The exhaust gases may then exit the energy recovery devicevia an outlet port 728 in a direction indicated by arrow 732, flowthrough the inlet exhaust manifold 706 coupled to the outlet port 728,and flow into the exchanger exhaust passages 709 internal to theinterior of the heat exchanger 700. In this way, the outlet port 728 ofthe energy recovery device is directly coupled to inlet exhaust manifold706 inside the heat exchanger 700. As such, exhaust gases flow directlyfrom the energy recovery device 704 to the interior of the heatexchanger 700.

A valve 785 internal to an interior of the energy recovery device 704may adjust a flow of exhaust gases from inlet port 726 towards theelectrically conductive element 784. For example, the valve 785 may bedisposed within a first device passage 786 while the electricallyconductive element 784 may be disposed within a second device passage788. The first device passage 786, second device passage 788, valve 785,and electrically conductive element 784 may each be included within aninterior of the energy recovery device 704.

In one example, the valve 785 may be opened to both of the inlet port726 and the first device passage 786 to increase a flow of exhaust gasin a direction indicated by arrow 787, but closed to the second devicepassage 788 to decrease a flow of exhaust gas in a direction indicatedby arrow 789. In this way, a flow of exhaust gas through the energyrecovery device 704 may not increase an output of the energy recoverydevice 704.

In a second example, the valve 785 may be opened to both of the inletport 726 and the second device passage 788 to increase a flow of exhaustgas in the direction indicated by arrow 789, but closed to the firstdevice passage 786 to decrease a flow of exhaust gas in the directionindicated by arrow 787. In this way, a flow of exhaust gas to theelectrically conductive element 784 may be increased, and the output ofthe energy recovery device 704 may increase.

In a third example, the valve may be opened or closed to each of theinlet port 726, the first device passage 786, and the second devicepassage 788 to increase or decrease the flow of exhaust gas in thedirections of arrows 787 and 789. In this way, a total flow of exhaustgases through the energy recovery device may be adjusted.

In the examples of opening or closing valve 785 as described above,opening or closing valve 785 (with respect to one or more correspondingpassages) may be include fully opening valve 785, fully closing valve785, or adjusting an amount of opening of valve 785 to a plurality ofpositions between fully open and fully closed. Additionally, when theenergy recovery device 704 is described as “active” or “operating”herein, an exhaust flow rate in the direction of arrow 788 (e.g., towardthe electrically conductive element) may be above a threshold flow rate.When the energy recovery device is described as “not active” or “notoperating” herein, an exhaust flow rate in the direction of arrow 788may be below a threshold flow rate.

During operation of the energy recovery device 704 (as described infurther detail below during the discussion of FIG. 10) the electricallyconductive element 784 of the energy recovery device 704 may be heatedvia contact with exhaust gases entering the inlet port 726. A portion ofthe thermal energy transferred to the electrically conductive element ofthe energy recovery device 704 is converted into electrical energy bythe energy recovery device 704. As a result, exhaust gases exiting theenergy recovery device 704 may have less thermal energy than the exhaustgases entering the energy recovery device 704 when the exhaust gas flowsin the direction of arrow 789 through the energy recovery device 704. Inother words, the exhaust gases exiting the outlet port 728 may be at alower temperature than the exhaust gases entering the inlet port 726while the energy recovery device 704 is active. In this way, the energyrecovery device 704 may be utilized to cool exhaust gases and generateelectrical energy for an engine system (such as the engine system 600shown by FIG. 6).

The outlet port 728 of the energy recovery device 704 is coupled to theinlet exhaust manifold 706, and the inlet exhaust manifold 706 iscoupled to the exchanger exhaust passages 709. Gases exiting the outletport 728 of the energy recovery device 704 flow through the inletexhaust manifold 706 into the exchanger exhaust passages 709. Theexchanger exhaust passages 709 then route the exhaust gas through theoutlet exhaust manifold 707 towards the exhaust outlet port 764 (coupledto the outlet exhaust manifold 707) in a direction indicated by arrow760.

The exhaust outlet port 764 is coupled to a passage 766 external to theinterior of the heat exchanger 700. Four-way valve 768 (e.g., such as4-way valve 650 shown by FIG. 6) is coupled to passage 766 (e.g., suchas third return passage 649 shown by FIG. 6), LP EGR passage 778 (e.g.,such as LP EGR passage 652 shown by FIG. 6), HP EGR passage 772 (e.g.,such as HP EGR passage 607 shown by FIG. 6), and exhaust return line 776(e.g., such as exhaust return line 651 shown by FIG. 6). Four-way valve768 may be actuated (e.g., opened or closed) by the controller toincrease or decrease a flow of gases from the exhaust outlet port 764 ofthe heat exchanger 700 through the passage 766 and into one or more ofthe HP EGR passage 772, the LP EGR passage 778, or the exhaust returnline 776, similar to the actuation of four-way valve 650 described abovein the discussion of FIG. 6.

As one example of actuation of four-way valve 768, the four-way valve768 may be opened to HP EGR passage 772 and opened to passage 766 toincrease a flow of gases from passage 766 through HP EGR passage 772,and closed LP EGR passage 778 to decrease the flow of gases through LPEGR passage 778, closed to exhaust return line 776 to decrease the flowof gases through exhaust return line 776, or closed to both of LP EGRpassage 778 and exhaust return line 776 to decrease flow of gases toboth of the LP EGR passage 778 and the exhaust return line 776. In thisconfiguration, the heat exchanger 700 routes exhaust gas in a directionindicated by arrow 770 to the intake system to provide HP EGR (asdescribed in the discussion of FIG. 6). As another example, the four-wayvalve 768 may be opened to LP EGR passage 778 to increase a flow ofgases through the LP EGR passage 778, and closed to HP EGR passage 772to decrease the flow of gases through HP EGR passage 772, closed toexhaust return line 776 to decrease the flow of gases through exhaustreturn line 776, or closed to both HP EGR passage 772 and exhaust returnline 776 to decrease the flow of gases through both HP EGR passage 772and the exhaust return line 776. In this configuration, the heatexchanger 700 routes exhaust gas in a direction indicated by arrow 780to the intake system to provide LP EGR. As yet another example, thefour-way valve 768 may be opened to exhaust return line 776 to increasea flow of gases through the exhaust return line 776, and closed to HPEGR passage 772 to decrease the flow of gases through HP EGR passage772, closed to LP EGR passage 778 to decrease the flow of gases throughLP EGR passage 778, or closed to both HP EGR passage 772 and LP EGRpassage 778 to decrease the flow of gases to both of the HP EGR passage772 and the LP EGR passage 778. In this configuration, the heatexchanger 700 routes exhaust gas in a direction indicated by arrow 774back to the exhaust system at a location upstream of the turbine viaexhaust return line 776 (e.g., similar to exhaust return line 651 shownby FIG. 6). As yet another example, the four-way valve 768 may be openedor closed to the LP EGR passage 778, the HP EGR passage 772, and theexhaust return line 776 to increase or decrease a flow of gases througheach of the LP EGR passage 778, HP EGR passage 772, and exhaust returnline 776, or the four-way valve 768 may be opened or closed to thepassage 766 to increase or decrease the flow of gases out of the exhaustoutlet port 764. In this configuration, the four-way valve 768 mayadjust flow of exhaust gas to each of the three passages mentionedabove.

In an example operation of the heat exchanger 700 according to thearrangement shown by FIG. 7 (and described above), exhaust flows intothe heat exchanger 700 via both the first exhaust inlet passage 716 andthe second exhaust inlet passage 710. The exhaust gas flows into theenergy recovery device 704 and transfers a first portion of thermalenergy to the energy recovery device 704. The energy recovery device 704converts an amount (based on an efficiency of the energy recoverydevice) of the first portion of thermal energy into electrical energyand stores the electrical energy in a battery (e.g., such as the battery602 shown by FIG. 6). The exhaust gas then flows out of the energyrecovery device 704 via the outlet port 728, through the inlet exhaustmanifold 706, and into the exchanger exhaust passages 709. Meanwhile,intake air from the intake system flows through intake air passage 734into the exchanger intake passages 703 via intake air inlet port 738.The exhaust gases flowing through the exchanger exhaust passages 709transfer a second portion of thermal energy to the intake air flowingthrough the exchanger intake passages 703 via proximity of the exchangerexhaust passages 709 to the exchanger intake passages 703. Through thisinteraction, the intake air increases in temperature while the exhaustgas decreases in temperature. Three-way valve 754 is then opened by thecontroller to the second SAI passage 756 to increase the flow of intakeair to the second SAI passage 756. The increased flow of intake airincreases the temperature of the second emissions control device viaexothermic reaction between intake air and exhaust gas in the exhaustsystem as described above. Four-way valve 768 is opened to the LP EGRpassage 778 by the controller to increase the flow of exhaust gas fromthe exchanger exhaust passages 709 through LP EGR passage 778 and to theintake system. The increased flow of exhaust gas to the intake systemprovides LP EGR and reduces noxious emissions from the exhaust system.

The above operation of the heat exchanger 700 is one example of flowingexhaust gases and intake air through the heat exchanger 700 according tothe configuration shown by FIG. 7 and is not a limiting case. Additionalmethods of operation are described in the discussion of FIGS. 10-12below. By adjusting flows of exhaust gas and intake air through the heatexchanger via actuation of valves coupled to the inlet and outlet portsof the heat exchanger (such as three-way valve 754 and four-way valve768), engine performance may be increased.

FIG. 8 shows a schematic representation of a third engine systemincluding a heat exchanger. Engine system 800 of FIG. 8 includes severalcomponents similar to those shown by engine system 600 of FIG. 6.Similar components between FIG. 6 and FIG. 8 may be labeled similarlyand may not be re-introduced in the discussion of FIG. 8 below.

Engine system 800 includes a control system 867. Control system 867 iscomprised of sensors 865, actuators 863, and a controller 869. Thesensors 865 may include several sensors (temperature sensors, pressuresensors, etc.) similar to those shown by FIG. 6 and may includeadditional sensors shown by FIG. 8 as described below. Similarly, theactuators 863 may include several actuators (e.g., actuators of valves)as described in the discussion of FIG. 6 and may include additionalactuators as described below. The controller 869 may comprise a similarstructure and configuration as the controller 669 shown by FIG. 6.However, the controller 869 includes additional instructions and/orlogic in non-transitory memory for controlling a flow of coolant withincomponents of engine system 800. In particular, controller 869 includesinstructions for adjusting coolant flow in response to a measured orestimated exhaust temperature (as described in the discussion of FIGS.11-12 below).

A heat exchanger 801 is coupled to both the intake system 670 and theexhaust system 672 of engine system 800 and includes an energy recoverydevice 604. In one example, the energy recovery device 604 is integratedwith the heat exchanger 801 such that the energy recovery device 604 isfluidly and physically coupled (e.g., directly coupled without anyintervening components separating the energy recovery device 604 and theheat exchanger 801) to the heat exchanger 801. The heat exchanger 801 ofengine system 800 is additionally fluidly coupled to a radiator 861. Theheat exchanger 801 is configured to receive coolant from the radiator861 and return coolant to the radiator 861. Coolant is routed within theheat exchanger 801 via a plurality of coolant passages (as shown by FIG.9 and described in the discussion of FIG. 9 below).

The heat exchanger 801 includes a coolant inlet port 864 and a coolantoutlet port 854. The coolant inlet port 864 is coupled to a firstcoolant passage 860, and the first coolant passage 860 is coupled to theradiator 861. A valve 862 is additionally coupled to the first coolantpassage 860 to adjust a flow of coolant to the heat exchanger 801. Forexample, valve 862 may be actuated (e.g., opened or closed) by thecontroller 869 to increase or decrease the flow of coolant from theradiator 861 to the heat exchanger 801 in response to operatingconditions of heat exchanger 801. A temperature sensor 858 is coupled tofirst coolant passage 860 and may transmit a signal to controller 869 toindicate a temperature of coolant within the first coolant passage 860.The heat exchanger 801 may return coolant to the radiator 861 via asecond coolant passage 856 coupled to both the heat exchanger 801 (viacoolant outlet port 854) and the radiator 861.

In an example operation of the heat exchanger 801 shown by FIG. 8, theheat exchanger 801 may receive intake air from the intake system 670 viaintake air passage 608, and may also receive exhaust gas from theexhaust system 672 via one or both of the first exhaust passage 616 andthe second exhaust passage 615. Intake air may flow out of the heatexchanger 801 via first return passage 629 and/or second return passage648, and exhaust gas may flow out of the heat exchanger 801 via thirdreturn passage 649. Additionally, coolant may flow to the heat exchanger801 via first coolant passage 860, and coolant may flow out of the heatexchanger 801 via second coolant passage 856. Coolant flow may increaseor decrease in response to operation of the energy recovery device 604and measured or estimated exhaust temperature (as described further inthe discussion of FIGS. 11-12 below). Within the heat exchanger, theintake air, exhaust gases, and coolant flow are all kept separate fromone another (via a plurality of passages of the heat exchanger) suchthat coolant flow, exhaust gas flow, and intake air flow, do not mixwith one another within the heat exchanger. In this way, only heat maytransfer between the coolant, exhaust gases, and intake air within theheat exchanger.

By adjusting coolant flow through the heat exchanger 801, thetemperature of intake air and exhaust gas flowing through the heatexchanger 801 may be adjusted. For example, the controller 869 mayincrease coolant flow to the heat exchanger 801 in order to decrease atemperature of exhaust gas flowing through the heat exchanger 801. Inthis way, EGR may be provided at a lower temperature and engineperformance may be increased.

FIG. 9 shows a third embodiment of a heat exchanger, such as the heatexchanger 801 shown by FIG. 8. The heat exchanger 900 shown by FIG. 9includes several components similar to those shown by heat exchanger 700of FIG. 7. Components shown by FIG. 9 that are also included within FIG.7 and have been introduced during the discussion of FIG. 7 may not bere-introduced in the following discussion of FIG. 9.

Heat exchanger 900 shown by FIG. 9 includes an energy recovery device704, a first plurality of passages 703 (which may herein be referred toas exchanger intake passages 703) coupled between an inlet intake airmanifold 705 and an outlet intake air manifold 708 internal to aninterior of a housing 902 of the heat exchanger 900, a second pluralityof passages 709 (which may herein be referred to as exchanger exhaustpassages 709) coupled between an inlet exhaust manifold 706 and anoutlet exhaust manifold 707 internal to the interior of the housing 902of the heat exchanger 900, and a plurality of passages and valvescoupling the heat exchanger 900 to both of an intake system (e.g.,intake system 670 shown by FIG. 8) and an exhaust system (e.g., exhaustsystem 672 shown by FIG. 8) in a configuration similar to that shown byheat exchanger 700 of FIG. 7. Heat exchanger 900 additionally includesthird plurality of passages 910 (which may herein be referred to asexchanger coolant passages 910) coupled between an inlet coolantmanifold 994 and an outlet coolant manifold 995 internal to the interiorof the housing 902 of the heat exchanger 900. Similar to the arrangementshown by FIG. 7 and discussed above with reference to FIG. 7, theexchanger exhaust passages 709 and exchanger intake passages 703 may bearranged perpendicular to each other. The exchanger coolant passages 910may be arranged perpendicular to each of the exchanger exhaust passages709 and exchanger intake passages 703 and an interface area between thethree pluralities of passages (exchanger exhaust passages 709, exchangerintake passages 703, and exchanger coolant passages 910) may include athermally conductive material (e.g., metal). In this way, thermal energymay transfer between intake air flowing through the exchanger intakepassages 703, exhaust gas flowing through the exchanger exhaust passages709, and coolant flowing through the exchanger coolant passages 910.

Coolant (e.g., from a radiator, such as the radiator 861 shown by FIG.8) flows through a coolant inlet passage 982 (e.g., such as the firstcoolant passage 860 shown by FIG. 8) in a direction indicated by arrow984. The flow of coolant through coolant inlet passage 982 is adjustedby a controller (such as the controller 869 shown by FIG. 8) viaactuation (e.g., opening or closing) of valve 988 (e.g., such as valve862 shown by FIG. 8) disposed within coolant inlet passage 982. Atemperature sensor 986 (e.g., such as temperature sensor 858 shown byFIG. 8) is coupled to the coolant inlet passage 982 and may transmit asignal to the controller to indicate a temperature of coolant flowingwithin the coolant inlet passage 982.

The coolant inlet passage 982 is coupled to a coolant inlet port 990 ofthe housing 902 of the heat exchanger 900. The coolant inlet port 990 isadditionally coupled to the inlet coolant manifold 994, and the inletcoolant manifold 994 is coupled to the exchanger coolant passages 910.Coolant may flow through the coolant inlet passage 982, into the coolantinlet port 990, and through the inlet coolant manifold 994 intoexchanger coolant passages 910. In this way, coolant may adjustably flow(via opening or closing of valve 988) from the radiator to the exchangercoolant passages 910 of the heat exchanger 900.

Coolant flows through the exchanger coolant passages 910 and is directedtowards the outlet coolant manifold 995 internal to the interior of thehousing 902. The outlet coolant manifold 995 is coupled to a coolantoutlet port 996 of the housing 902, and the coolant outlet port 996 isadditionally coupled to a coolant outlet passage 998 external to theinterior of the housing 902. Coolant may flow from the exchanger coolantpassages 910, through the outlet coolant manifold 995, into the coolantoutlet port 996, and through the coolant outlet passage 998 in adirection indicated by arrow 997.

By configuring the heat exchanger 900 with the exchanger coolantpassages 910 in this way, the exchanger coolant passages 910 mayselectively receive coolant from the radiator via the inlet coolantmanifold 994 coupled to the coolant inlet port 990 of the housing 902and may return coolant to the radiator via the outlet coolant manifold995 coupled to the coolant outlet port 996 of the housing 902. Thecoolant may receive thermal energy from intake air flowing through theexchanger intake passages 703 and/or exhaust gas flowing through theexchanger exhaust passages 709, and the coolant may transfer thermalenergy to the radiator. The controller may adjust coolant flow throughthe radiator (as described in the discussion of FIGS. 11-12 below) viaopening or closing of valve 982 in order to adjust an amount of thermalenergy exchange (e.g., adjust a temperature) between the coolant, intakeair, and exhaust gas. In this way, engine performance may be increased.

FIG. 10 shows a method 1000 for adjusting operation of an energyrecovery device (such as the energy recovery device 704 shown by FIG. 7and FIG. 9) coupled to a heat exchanger (such as the heat exchanger 601shown by FIG. 6, or the heat exchanger 801 shown by FIG. 8) in responseto operating conditions of an engine (such as the engine 168 shown byFIG. 6 and FIG. 8). The method includes increasing, maintaining, ordecreasing an output of the energy recovery device via a controller(such as the controller 669 shown by FIG. 6, or the controller 869 shownby FIG. 8) based on signals from sensors (such as the sensors 665described during the discussion of FIG. 6, or the sensors 865 of FIG. 8)of an engine system (such as the engine system 600 shown by FIG. 6, orthe engine system 800 shown by FIG. 8).

The method at 1002 includes estimating and/or measuring engine operatingconditions based on one or more outputs of various sensors within in theengine system (e.g., such as various temperature sensors, pressuresensors, etc., as described above) and/or operating conditions of theengine system. Engine operating conditions may include engine speed andload, EGR flow rate (LP and/or HP), mass air flow rate, turbine speed,compressor inlet pressure, emissions control device temperature, coolantflow rate, a demand of one or more electrical components of the engine,exhaust temperatures, intake air temperatures, etc. The operatingconditions may also include the operating conditions of the heatexchanger (e.g., energy recovery device electrical output, temperatureof exhaust gases within the exhaust system, flow rate of gases throughthe heat exchanger, etc.).

The method continues to 1004 where the method includes detecting whetherthe engine is in a cold start condition. A cold start condition mayinclude adjusting the engine from a non-operational state to anoperational state while a temperature of the engine is below a thresholdtemperature. The threshold temperature may be based on a standardoperating temperature of the engine during prolonged periods of low tomoderate engine load. As an example, the temperature of the engine maybe estimated based on a signal transmitted to the controller from one ormore sensors configured to detect a temperature of coolant circulatingwithin the engine. The controller may compare the estimated value ofengine temperature to the threshold value in order to determine whetherthe engine is in a cold start condition.

If the controller determines the engine is in a cold start condition at1004, the method continues to 1014 where the method includes decreasingan output of the energy recovery device of the heat exchanger. Theoutput of the energy recovery device includes an electrical currentgenerated by the energy recovery device. The electrical current isgenerated in response to a transfer of thermal energy to the energyrecovery device from exhaust gas flowing through the energy recoverydevice. If the output of the energy recovery device cannot be furtherdecreased (for example, if the output is at a minimum output), thecontroller may maintain the minimum output of the energy recoverydevice. In another example, the method at 1014 may include turning offthe energy recovery device so that no thermal energy is extracted fromexhaust gases passing through the energy recovery device and to the heatexchanger.

For example, an amount of thermal energy transferred to the energyrecovery device from the exhaust gas may be proportional to atemperature and mass flow rate of the exhaust gas. As a result, theelectrical current generated by the energy recovery device may also beproportional to the temperature and mass flow rate of the exhaust gas.During a cold start condition, the exhaust mass flow rate through anexhaust system may be decreased compared to an exhaust mass flow rateduring average engine operating conditions (e.g., low to moderate engineload for a prolonged period of time). As a result, an exhaust mass flowrate through the heat exchanger (and energy recovery device) may also bedecreased during a cold start condition. The reduced exhaust flow ratethrough the heat exchanger results in a decreased amount of thermalenergy available to the heat exchanger from exhaust gas flow during acold start condition compared to an amount of thermal energy availableto the heat exchanger from exhaust gas flow during engine runningconditions when engine temperatures are above a threshold (e.g., coldstart thresholds as described above). In response to the cold startcondition, the controller may decrease the output of the energy recoverydevice in order to decrease the amount of thermal energy transferredaway from exhaust gas flowing into the heat exchanger (e.g., to decreasecooling of the exhaust gas).

As one example, by decreasing the output of the energy recovery devicein this way during a cold start condition, exhaust gas flowing out ofthe energy recovery device and into exchanger exhaust passages (such asthe exchanger exhaust passages 709 shown by FIG. 7 and FIG. 9) maypreserve an increased amount of thermal energy compared to exhaust gasthat flows through the energy recovery device when output is notdecreased. In one example, the preserved thermal energy of the exhaustgas may be utilized by the heat exchanger to heat intake air flowingthrough exchanger intake passages (such as exchanger intake passages 703shown by FIG. 7 and FIG. 9). In this way, intake air for secondary airinjection may be provided to the exhaust system at a higher temperatureto increase an efficiency of an exothermic reaction (as described abovein the discussion of FIG. 7).

In an example of decreasing the output of the energy recovery device,the output (e.g., generated electrical current) of the energy recoverydevice may be decreased by diverting a portion of exhaust gas away froman element of the energy recovery device configured to receive thermalenergy from the exhaust gas. The exhaust gas may be diverted viaactuation of a valve (not shown) internal to an interior of the energyrecovery device by the controller. By adjusting a position (e.g., anamount of opening) of a valve internal to the energy recovery device(such as the valve 785 shown by FIG. 7 and FIG. 9 and described above)via the controller, an amount of exhaust gas flow diverted from theenergy recovery device and into the exchanger exhaust passages may beadjusted. In this way, decreasing the amount of opening of the valvedecreases the output of the energy recovery device.

If a cold start is not detected at 1004, the method continues to 1006where the method includes determining whether the engine load is lessthan a threshold engine load. As an example, engine load may bedetermined based on engine torque output. In one example, the thresholdengine load may be based on an engine torque output typical of amoderate engine operational speed. In another example, the thresholdengine load may be indicative of a relatively low engine load whereexhaust temperatures and/or exhaust gas flow rates through an exhaustpassage may be reduced. One or more sensors coupled to the engine, suchas a manifold pressure sensor, temperature sensor, and/or a mass flowsensor, may transmit information (e.g., signals) to the controller. Thecontroller may interpret signals from one or more of the sensors todetermine engine load.

If the engine load is determined by the controller to be below thethreshold engine load at 1004, the method continues to 1014 where themethod includes decreasing an output of the energy recovery device ofthe heat exchanger, as explained above.

During periods of low engine load (e.g., periods in which measuredengine load is lower than the threshold engine load), exhaust mass flowrate may be decreased compared to periods of moderate or high engineload. As a result, the controller may decrease output of the energyrecovery device in order to preserve thermal energy of the exhaust gasflowing out of the energy recovery device (as described above). In thisway, exhaust gas flowing through the exchanger exhaust passages maytransfer thermal energy to intake air flowing through the exchangerintake passages. The exhaust gas may then be returned to the exhaustsystem at a relatively higher temperature by decreasing energy deviceoutput compared to exhaust gases returned to the exhaust system withoutdecreasing energy device output.

If the measured engine load is determined to be at or greater than thethreshold engine load at 1006, the method continues to 1008 where themethod includes determining whether a temperature of the exhaust gas isless than a threshold exhaust temperature. The temperature of theexhaust gas may be measured by one or more sensors coupled to theexhaust system, such as (but not limited to) the temperature sensor 189shown by FIG. 6 and FIG. 8. In one example, the threshold exhausttemperature may be based on a temperature for efficient operation of theenergy recovery device. As described in the discussion of FIG. 6, afirst side of the energy recovery device may be held at a temperaturelower than a second side of the energy recovery device in order toincrease a temperature gradient (e.g., temperature difference) acrossthe device. In this case, the threshold exhaust temperature may be basedon a temperature determined by the controller to sufficiently heat thesecond side of the energy recovery device to a threshold operationaltemperature.

If the exhaust temperature is determined by the controller to be belowthe threshold exhaust temperature at 1008, the method continues to 1014where the method includes decreasing an output of the energy recoverydevice of the heat exchanger, as explained above. For example, thecontroller may decrease output of the energy recovery device until theexhaust temperature entering the heat exchanger has increased to thethreshold exhaust temperature in order to provide efficient operation ofthe energy recovery device.

If the measured exhaust temperature is determined to be at or greaterthan the threshold exhaust temperature at 1008, the method continues to1010 where the method includes determining whether regeneration of adiesel particulate filter (DPF) or a gasoline particulate filter (GPF)is active. For example, prior to the determination at 1010, thecontroller may have initiated regeneration of an engine particulatefilter (DPF for an engine utilizing diesel fuel, or GPF for an engineutilizing gasoline fuel).

If the controller determines that the regeneration of the engineparticulate filter is active at 1010, the method continues to 1014 wherethe method includes decreasing an output of the energy recovery deviceof the heat exchanger, as explained above. Decreasing the output of theenergy recovery device of the heat exchanger in response to an activeregeneration of the engine particulate filter may result in an increasedtemperature of exhaust gases flowing out of the heat exchanger. Theincreased temperature of the exhaust gases may increase the efficiencyof the regeneration of the engine particulate filter.

If the controller determines that the regeneration of the engineparticulate filter is not active at 1010, the method continues to 1012where the method includes increasing or maintaining an output of theenergy recovery device of the heat exchanger. In one example, the enginemay be operating with an increased engine load and/or an increasedexhaust temperature. The output of the energy recovery device may beincreased in order to utilize the additional thermal energy supplied tothe heat exchanger. In a second example, the controller may increaselow-pressure EGR flow and/or high-pressure EGR flow as engine loadincreases and/or in response to additional engine operating conditions.In this case, the output of the energy recovery device may be increasedto reduce the temperature of the exhaust gas flowing out of the energyrecovery device in order to reduce a temperature of exhaust gases forEGR injection. In a third example, the engine may be operating with arelatively constant engine load for a prolonged period of time and thecontroller may have implemented an efficient rate of output for theenergy recovery device according to the engine load. In this situation,the output of the energy recovery device may be maintained (e.g., notadjusted by the controller) in order to continue to provide an efficientamount of electrical energy generation to the engine system.

FIG. 11 shows a method 1100 for adjusting flow of intake air, exhaustgas, and/or coolant through a heat exchanger (such as the heat exchanger700 shown in FIG. 7 and/or the heat exchanger 900 shown by FIG. 9) inresponse to an output of an energy recovery device (such as energyrecovery device 704 shown by FIGS. 7 and 9). As described below,adjustment of one or more flows may be based on an exhaust temperatureat a location within an exhaust system. Alternately, adjustment of oneor more flows may be based on an estimated temperature of exhaust gaseswithin the heat exchanger according to energy recovery device output.

At 1102, the method includes estimating and/or measuring engineoperating conditions based on one or more outputs of various sensors inthe engine system and/or operating conditions of the engine system(e.g., such as various temperature sensors, pressure sensors, etc., asdescribed above). Engine operating conditions may include engine speedand load, EGR flow rate (LP and/or HP), mass air flow rate, turbinespeed, compressor inlet pressure, emissions control device temperature,coolant flow rate, etc. The operating conditions may also include theoperating conditions of the heat exchanger (e.g., energy recovery deviceelectrical output, temperature of exhaust gases and/or intake air nearthe heat exchanger, flow rate of gases through the heat exchanger,etc.).

At 1104 the method includes determining whether an output of the energyrecovery device is greater than a threshold output. As described abovein the discussion of FIG. 10, the output of the energy recovery deviceincludes an electrical current generated by the device in response to atemperature gradient across the device (e.g., a temperature differencebetween a first side of the device and a second side of the device). Asthe magnitude of the temperature gradient across the device increases,the electrical current generated by the device also increases. In otherwords, the output of the device is proportional to an amount of thermalenergy transferred to the device.

The threshold output (e.g., threshold electrical current) may correspondto a specific magnitude of electrical current generated by the device.For example, a controller (such as the controller 869 shown by FIG. 8)may receive an electrical signal from the energy recovery device. Thecontroller may then compare the magnitude of the received electricalcurrent to the threshold electrical current in order to determinewhether the received electrical current is greater than the thresholdelectrical current. The threshold electrical current may be based inpart on a minimum electrical current that indicates that the energyrecovery device is operating and removing thermal energy from exhaustgases passing through the energy recovery device. In one example, thethreshold electrical current may be a non-zero threshold. In anotherexample, threshold electrical current may be substantially zero suchthat when the energy recovery device output is above threshold it isoperating and producing current via removing heat from exhaust gasespassing through the device.

If the controller determines at 1104 that the output of the energyrecovery device is not greater than the threshold output, the methodcontinues to 1106 where the method includes adjusting one or more ofintake, exhaust, or coolant flows through the heat exchanger based on atemperature of exhaust gas within the exhaust system, upstream of theheat exchanger. For example, the controller may receive a signal fromone or more temperature sensors coupled to the exhaust system at one ormore locations (e.g., coupled to an exhaust manifold, coupled downstreamof a first emissions control device, etc.). The controller may utilizethe signals from the temperature sensors to determine the temperature ofexhaust gas flowing through the exhaust system. In response to thedetermined temperature, the controller may adjust a flow of intake air,exhaust gas, and/or coolant through the heat exchanger via actuation ofone or more valves coupled to the heat exchanger (e.g., such as thefour-way valve 633 shown by FIG. 6 and FIG. 8).

In one example, the controller may increase coolant flow through theheat exchanger in response to the determined temperature (as describedabove) in order to cool one or more of the intake air and exhaust gasflowing through the heat exchanger, or the controller may decreasecoolant flow through the heat exchanger in order to increase atemperature of one or more of the intake air and exhaust gas flowingthrough the heat exchanger. While the energy recovery device operateswith an output below the threshold output, a decreased amount of thermalenergy is transferred away from exhaust gas flowing through the energyrecovery device. The adjustment of coolant flow through the heatexchanger by the controller may compensate for a reduced cooling effectof the energy recovery device due to the reduced output of the energyrecovery device.

In another example, the controller may increase intake air flow throughthe heat exchanger in response to the determined temperature of exhaustgas in the exhaust system in order to decrease a temperature of exhaustgas flowing through the heat exchanger, or the controller may decreaseintake air flow through the heat exchanger in order to increase thetemperature of exhaust gas flowing through the heat exchanger. In thisway, the flow of intake air through the heat exchanger may provide anadditional method of adjusting the temperature of exhaust gas flowingthrough the heat exchanger. The flow of intake air may also be utilizedto adjust the temperature of exhaust gas flowing through a heatexchanger that does not include coolant flow (e.g., such as theembodiment of the heat exchanger 700 shown by FIG. 7).

In yet another example, adjusting the flow of exhaust gas through theheat exchanger may adjust the temperature of the intake air flowingthrough the heat exchanger. The controller may increase a flow ofexhaust gas through the heat exchanger in order to increase atemperature of intake air flowing through the heat exchanger, or thecontroller may decrease the flow of exhaust gas through the heatexchanger in order to decrease the temperature of intake air flowingthrough the heat exchanger. The increased temperature of the exhaust gasflowing through the heat exchanger due to the decreased amount ofthermal energy transferred away from exhaust gas by the energy recoverydevice enables a more efficient heating of the intake air flowingthrough the heat exchanger.

If the controller determines at 1104 that the output of the energyrecovery device is not lower than the threshold output, the methodcontinues to 1108 where the method includes estimating exhaust gastemperature entering the heat exchanger from the energy recovery devicebased on an output of the energy recovery device. In other words, whenthe electrical current generated by the energy recovery device isgreater than a threshold electrical current, the controller may estimatethe temperature of exhaust gas entering and flowing through the heatexchanger based on a magnitude of the electrical current generated bythe energy recovery device.

As described above, the magnitude of the electrical current generated bythe energy recovery device may be proportional to a temperaturedifference between a first side of the device and a second side of thedevice. The first side of the device may be in approximate thermalequilibrium with a first temperature reservoir (as described above inthe discussion of FIG. 6) such as ambient air, engine coolant, etc., andthe temperature of the first temperature reservoir may be determined bythe controller via signals from one or more temperature sensors arrangedproximate to the first temperature reservoir. The magnitude of theelectrical current generated by the energy recovery device can then beinterpreted by the controller in order to calculate a difference intemperature between the first side of the energy recovery device and thesecond side of the energy recovery device based on instructions storedin a non-transitory memory of the controller. The controller may thenestimate the temperature of exhaust gases flowing through the heatexchanger based on the calculated difference in temperature between thefirst side of the energy recovery device and the second side of theenergy recovery device.

After the controller has estimated the temperature of exhaust gasflowing through the heat exchanger at 1108, the method continues to 1110where the method includes adjusting one or more of intake air, exhaustgas, or coolant flows through the heat exchanger based on the estimatedtemperature of exhaust gas. As described above (e.g., with reference to1106), adjusting one or more of coolant flow, intake air flow, orexhaust gas flow through the heat exchanger may adjust a temperature ofthe intake air and/or the exhaust gas flowing through the heatexchanger.

In one example of the method at 1110, as shown at 1112, the methodincludes adjusting the intake air flow through the heat exchanger basedon the estimated temperature of exhaust gas. For example, the intake airflow may be increased in order to decrease the temperature of theexhaust gas, or the intake air flow may be decreased in order toincrease the temperature of the exhaust gas. As one example, increasingthe intake air flow may include adjusting an amount of opening of avalve coupled to an intake air outlet of the heat exchanger. The valve(such as three-way valve 754 or valve 748 shown by FIG. 7 and FIG. 9)may be opened or closed to a passage coupled between the heat exchangerand one of either an intake system or the exhaust system.

In a first example of adjusting intake air flow through the heatexchanger based on the estimated temperature of exhaust gas, if theestimated temperature of exhaust gas is above a threshold temperature,intake air flow may be increased in order to heat the intake air forsecondary air injection into the exhaust system (e.g., to increase anefficiency of the SAD, or decreased in order to increase a flow ofintake air through the intake system (e.g., increasing intake air flowthrough the intake system by decreasing an amount directed toward theheat exchanger).

In a second example of adjusting intake air flow through the heatexchanger based on the estimated temperature of exhaust gas, if theestimated temperature of exhaust gas is below the threshold temperature,intake air flow may be increased in order to reduce a risk of compressorsurge without appreciably heating the intake air (e.g., by reducingthermal energy exchange between the intake air and exhaust gas), ordecreased in order to increase the flow of intake air through the intakesystem (as described above).

In another example of the method at 1110, at 1114 the method includesadjusting the exhaust gas flow through the heat exchanger based on theestimated temperature of the exhaust gas. For example, the exhaust gasflow may be increased in order to increase an amount of thermal energytransferred to the energy recovery device and/or to increase atemperature of the intake air flowing through the heat exchanger. Inother words, an increase in exhaust flow may increase an output of theenergy recovery device. As another example, the exhaust gas flow may bedecreased if controller determines that transfer of thermal energy tothe energy recovery device be decreased (e.g., if a battery coupled tothe energy recovery device is fully charged), and/or a decrease in thetemperature of the intake air flowing through the heat exchanger isdesired. As one example, increasing the exhaust gas flow may includeadjusting an amount of opening of a valve coupled to an exhaust gasoutlet of the heat exchanger. The valve (such as four-way valve 768shown by FIG. 7 and FIG. 9) may be opened or closed to one or morepassages coupled between the heat exchanger and the intake system and/orthe exhaust system.

In a first example of adjusting exhaust gas flow through the heatexchanger based on the estimated temperature of exhaust gas, if theestimated temperature of exhaust gas is above the threshold temperature,exhaust gas flow may be increased in order to increase the output of theenergy recovery device (e.g., to increase an amount of exhaust gastransferring thermal energy to the energy recovery device) or toincrease an efficiency of a second emissions control device arrangedwithin the exhaust system (e.g., to reduce an operating temperature ofthe second emissions control device below a threshold temperature forefficient NOx removal from exhaust gas, for example), or decreased inorder to increase an amount of cooling of the exhaust by the intake airand/or coolant in order to supply the cooled exhaust to the intakesystem as HP EGR (e.g., by decreasing an amount of exhaust gas flowingthrough the heat exchanger, the temperature of the exhaust gas isadjusted more quickly by the flows of intake air and/or coolant).

In a second example of adjusting exhaust gas flow through the heatexchanger based on the estimated temperature of exhaust gas, if theestimated temperature of exhaust gas is below the threshold temperature,exhaust gas flow may be increased in order to increase the output of theenergy recovery device (e.g., if a threshold charge of the battery or athreshold electrical demand of engine system has not been met), ordecreased in order to increase an efficiency of the second emissionscontrol device (e.g., by increasing the operating temperature of thesecond emissions control device above a threshold temperature forefficient NOx removal from exhaust gas, for example).

In yet another example of the method at 1110, at 1116 the methodincludes adjusting the coolant flow through the heat exchanger based onthe estimated temperature of the exhaust gas if the heat exchanger isconfigured for coolant flow (e.g., such as the heat exchanger 900 shownby FIG. 9). For example, although the energy recovery device receivesthermal energy from the exhaust gas (and lowers the temperature of theexhaust gas), in some situations additional cooling may be desired(e.g., in order to provide more efficient EGR to the engine). As oneexample, increasing the coolant flow may include adjusting an amount ofopening of a valve coupled to a coolant outlet of the heat exchanger.The valve (such as valve 988 shown by FIG. 9) may be opened or closed toa passage coupled between the heat exchanger and a radiator.

In a first example of adjusting coolant flow through the heat exchangerbased on the estimated temperature of exhaust gas, if the estimatedtemperature of exhaust gas is above the threshold temperature, coolantflow may be increased in order to increase an amount of cooling of theexhaust gas by the coolant (e.g., to lower the temperature of theexhaust gas for EGR injection in order to reduce engine degradation), ordecreased in order to reduce the amount of cooling of the exhaust gas bythe coolant (to increase the transfer of thermal energy from the exhaustgas to the intake air for secondary air injection, for example).

In a second example of adjusting exhaust gas flow through the heatexchanger based on the estimated temperature of exhaust gas, if theestimated temperature of exhaust gas is below the threshold temperature,coolant flow may be increased in order to provide additional cooling ofthe exhaust gas (e.g., for EGR injection as described above), ordecreased if additional cooling is not desired (e.g., if the energyrecovery device is sufficiently cooling the exhaust gas via transfer ofthermal energy from the exhaust gas to the energy recovery device).

By determining an adjustment to flows of intake air, exhaust gas, and/orcoolant flow based on either the estimated exhaust temperature withinthe heat exchanger or the measured exhaust temperature within theexhaust system (with determination made in response to energy recoverydevice output), the temperature of exhaust gas flowing from the heatexchanger may be controlled with increased precision. For example, theestimated exhaust temperature provides the controller with additionalinformation about the condition of gases flowing through the heatexchanger (e.g., information additional to the temperature of theexhaust gas as it was measured before flowing into the energy recoverydevice of the heat exchanger). In this way, the controller may moreprecisely adjust flows of intake air and exhaust gas from the heatexchanger in order to provide EGR injection and secondary air injectionat desired temperatures to increase engine performance.

FIG. 12 shows a graphical example of adjustments to an output of anenergy recovery device (e.g., such as the energy recovery device 704shown by FIGS. 7 and 9) in response to engine operating conditions, aswell as adjustments to one or more of intake air flow, exhaust gas flow,or coolant flow through a heat exchanger (e.g., such as the heatexchanger 900 shown by FIG. 9) in response to energy recovery deviceoutput (which may be an amount of electrical current output by theenergy recovery device, in one example).

Specifically, graph 1200 shows changes in engine torque output at plot1202, changes in energy recovery device output at plot 1206, changes inexhaust temperature within an exhaust system upstream of the heatexchanger at plot 1210, changes in estimated exhaust temperatureentering the heat exchanger at plot 1212 and plot 1214, changes inintake air flow through the heat exchanger at plot 1216, changes inexhaust flow through the heat exchanger at plot 1218, and changes incoolant flow through the heat exchanger at plot 1220.

The exhaust temperature in the exhaust system may be determined by acontroller (such as controller 869 shown by FIG. 8) based on a signalfrom one or more temperature sensors coupled to the exhaust system. Theintake air flow, exhaust air flow, and coolant flow to the heatexchanger may all be delivered by a plurality of passages arrangedbetween the heat exchanger and a radiator, an intake system, and theexhaust system (and by adjustments to valves disposed within thosepassages), such as the passages described above with reference to FIGS.6-9.

The controller may actuate actuators coupled to the various valves inorder to adjust the flow of intake air, exhaust gas, and/or coolant tothe heat exchanger from the intake system, exhaust system, and radiator,respectively, as described below.

Prior to time t1, engine torque output is increasing (plot 1202).Temperature of exhaust gas within the exhaust system (plot 1206) is alsoincreasing. In one example, the increase in engine torque output andincrease in temperature of exhaust gas within the exhaust system may bea result of an engine cold start (e.g., the engine adjusted from anon-operational state to an operational state). Despite the increase inexhaust temperature, the temperature of the exhaust gas within theexhaust system is below a threshold temperature (plot 1214). As aresult, the output of the energy recovery device (plot 1206) is below athreshold output (plot 1208). In response to the output of the energyrecovery device, the flow of intake air through the heat exchanger (plot1216), the flow of exhaust gas through the heat exchanger (plot 1218),and the flow of coolant through the heat exchanger (plot 1220) areadjusted based on the temperature of the exhaust gas in the exhaustsystem. Specifically, the flow of each of intake air, exhaust gas, andcoolant increases.

Between time t1 and t2, the engine torque output (plot 502) remainsrelatively constant, and the engine is indicated to possess a relativelylow load. This may correspond to a warm-up phase of the engine, and/oror a cruising phase in which torque output remains low. The enginetorque output is below a threshold torque output (plot 1204) betweentime t1 and t2. Additionally, the temperature of exhaust gas in theexhaust system (plot 1210) is below a threshold exhaust temperature(plot 1215). In response to both the low (e.g., below threshold) enginetorque output and the low temperature of exhaust gas in the exhaustsystem, the output of the energy recovery device (plot 1206) is notincreased. Although the temperature of exhaust gas in the exhaust systemis below the threshold temperature between time t1 and t2, thetemperature of the exhaust gas continues to increase. Intake air flow,exhaust gas flow, and coolant flow through the heat exchanger eachcontinue to increase in response to the temperature of the exhaust gaswithin the exhaust system.

At time t2, engine torque output (plot 1202) reaches the thresholdtorque output (plot 1204). Additionally, temperature of exhaust gas inthe exhaust system (plot 1210) reaches the threshold exhaust temperature(plot 1215). Between time t2 and t3, engine torque output (plot 1202)and the temperature of exhaust gas in the exhaust system (plot 1210)continue to increase. In response to the increased torque output andincreased exhaust temperature (e.g., the torque output exceeding thethreshold torque output, and the exhaust temperature exceeding thethreshold exhaust temperature), the output of the energy recovery device(plot 1206) increases. Intake air flow (plot 1216) and exhaust gas flow(plot 1218) to the heat exchanger remain approximately constant whilecoolant flow (plot 1220) increases slightly in response to theincreasing temperature of the exhaust gas within the exhaust system.

At time t3, the output of the energy recovery device (plot 1206) reachesthe threshold output (plot 1208). Between time t3 and t4, engine torqueoutput (plot 1202) remains approximately constant above the thresholdtorque output (plot 1204). The controller estimates a temperature ofexhaust gas within the heat exchanger (plot 1212) in response to theincreased output of the energy recovery device (e.g., in response to theoutput of the device exceeding the threshold output). The estimatedexhaust temperature is initially lower than the temperature of exhaustgas in the exhaust system (plot 1210) due to the transfer of thermalenergy from the exhaust gas to the energy recovery device (as describedabove in the discussion of FIGS. 10-11). As the output of the energyrecovery device increases, the difference between the temperature of theexhaust gas in the exhaust system and the estimated temperature of theexhaust gas in the heat exchanger also increases. In other words, as theoutput of the energy recovery device increases, the estimatedtemperature of the exhaust gas in the heat exchanger is decreasedrelative to the measured temperature of exhaust gas in the exhaustsystem (due to the transfer of energy described above). The flows ofintake air, exhaust gas, and coolant through the heat exchanger betweentime t2 and t3 are each adjusted in response to the estimatedtemperature of exhaust gas within the heat exchanger (e.g., the flowsare not adjusted based on the measured temperature of exhaust gas withinthe exhaust system). Specifically, flow of intake air to the heatexchanger (plot 1216) decreases in response to the estimated exhausttemperature, exhaust gas flow to the heat exchanger (plot 1218)increases in response to the estimated exhaust temperature, and coolantflow to the heat exchanger (plot 1220) slightly increases in response tothe estimated exhaust temperature. The increase in exhaust gas flow anddecrease in intake air flow may be the result of the reduced estimatedexhaust temperature within the heat exchanger relative to the measuredexhaust temperature within the exhaust system.

Between time t4 and t5, engine torque output (plot 1202) sharplyincreases. In one example, the increase in engine torque output may beaccompanied by a signal from the controller to the engine to initiate aregeneration of an engine particulate filter (e.g., a diesel particulatefilter, gasoline particulate filter, etc.) due to an anticipatedincrease in exhaust gas temperature. In response to the particulatefilter regeneration, the output of the energy recovery device (plot1206) decreases (as described in the discussion of FIG. 10). However,between time t4 and t5, the output of the energy recovery device isabove the threshold output (plot 1208), and in response, the controllercontinues to estimate the temperature of exhaust gas within the heatexchanger (plot 1212). As the output of the energy recovery devicedecreases, the estimated exhaust gas temperature within the heatexchanger approaches the measured exhaust temperature within the exhaustsystem (plot 1210). The estimated exhaust temperature and the measuredexhaust temperature between t4 and t5 both increase due to the increasedengine torque output. In response to the increased estimated exhausttemperature, the controller increases the flow of intake air through theheat exchanger (plot 1216) and increases the flow of coolant through theheat exchanger (plot 1220). The controller also decreases the flow ofexhaust gas through the heat exchanger (plot 1218).

At time t5, the output of the energy recovery device (plot 1206)decreases below the threshold output (plot 1208). Between time t5 andt6, engine torque output (plot 1202) continues to increase. In responseto the output of the energy recovery device decreasing below thethreshold output at t5, the controller does not continue to estimate thetemperature of exhaust gas within the heat exchanger between time t5 andt6. Additionally, the intake air flow (plot 1216), exhaust gas flow(1218), and coolant flow (plot 1220) through the heat exchanger areadjusted by the controller in response to the measured temperature ofexhaust gas within the exhaust system (plot 1210). For example, themeasured temperature of exhaust gas in the exhaust system between timet5 and t6 is greater than the last estimated temperature of exhaust gaswithin the heat exchanger at time t5. In response to the relativeincrease in exhaust temperature (e.g., the measured temperature comparedto the previously estimated temperature), the controller increasesintake air flow and coolant flow through the heat exchanger and reducesexhaust gas flow through the heat exchanger.

At time t6, engine torque output (plot 1202) stops increasing and beginsto decrease. In one example, the change in engine torque output may beaccompanied by a conclusion of the regeneration of the engineparticulate filter (as described above). In response to the conclusionof the particulate filter regeneration, energy recovery device output(plot 1206) begins to increase. Between time t6 and time t7, enginetorque output is decreasing, energy device output is increasing, and thetemperature of exhaust gas within the exhaust system (plot 1210) isincreasing (e.g., increasing due to residual heat from particulatefilter regeneration). The energy recovery device output is below thethreshold output (plot 1208), and in response, the intake air flow (plot1216), exhaust gas flow (plot 1218), and coolant flow (plot 1220)through the heat exchanger are adjusted based on the temperature ofexhaust within the exhaust system. The intake air flow and exhaust gasflow are slightly adjusted (e.g., increased and decreased, respectively)but remain relatively constant. The coolant flow is increased.

At time t7, energy recovery device output (plot 1206) increases to thethreshold output (plot 1208). Between time t7 and t8, engine torqueoutput (plot 1202) is decreasing and the temperature of exhaust gaswithin the exhaust system (plot 1210) is decreasing. Energy recoverydevice output increases and then remains relatively constant as intakeair flow (plot 1216), exhaust gas flow (plot 1218), and coolant flow(plot 1220) through the heat exchanger are each adjusted in response toan estimated exhaust temperature within the heat exchanger (plot 1214).The estimated exhaust temperature is generated by the controller (asdescribed above with reference to the estimated exhaust temperatureshown by plot 1212) in response to the output of the energy recoverydevice surpassing the threshold output at t7. As the output of theenergy recovery device increases, the amount of thermal energytransferred away from the exhaust gas entering the heat exchanger alsoincreases. As a result, a difference between the estimated temperatureof the exhaust gas within the heat exchanger and the measuredtemperature of exhaust gas within the exhaust system increases in unisonwith the energy recovery device output. In other words, as the energyrecovery device output increases, the estimated temperature of exhaustgas within the heat exchanger decreases relative to the measured exhaustgas temperature. In response to the decreasing estimate of exhausttemperature within the heat exchanger, the controller decreases theintake air flow (plot 1216) to the heat exchanger, increases the exhaustgas flow (plot 1218) to the heat exchanger, and decreases the coolantflow (plot 1220) to the heat exchanger.

At time t8, the engine torque output (plot 1202) decreases below thethreshold torque output (plot 1204). Between times t8 and t9, inresponse to the engine torque output decreasing below the thresholdtorque output at time t8, the engine recovery device output (plot 1206)begins to decrease. As a result of the energy recovery device outputdecreasing, the estimated exhaust temperature within the heat exchanger(plot 1214) begins to approach the measured temperature of exhaustwithin the exhaust system (plot 1210). However, due to the decreasedengine torque output, both the estimated exhaust temperature and themeasured exhaust temperature are decreasing between times t8 and t9. Inresponse to the decreasing estimate of exhaust temperature within theheat exchanger, the controller increases the exhaust gas flow (plot1218) to the heat exchanger, increases the intake air flow (plot 1216)to the heat exchanger, and decreases the coolant flow (plot 1220) to theheat exchanger. In one example, the exhaust flow and intake flow may beincreased in order to reduce a risk of compressor surge as indicated bythe decreasing estimate of exhaust temperature within the heatexchanger.

At time t9, the engine torque output (plot 1202) has increased above thethreshold torque output (plot 1204). After time t9, the engine torqueoutput remains approximately constant with occasional smallfluctuations. The output of the energy recovery device (plot 1206)increases and then remains approximately constant above the thresholdoutput (plot 1208). In response to the output of the energy recoverydevice, the controller continues to estimate the temperature of exhaustgas within the heat exchanger (plot 1214). The controller adjusts theflows of intake air flow (plot 1216), exhaust gas flow (plot 1218), andcoolant flow (plot 1220) in response to the estimated exhausttemperature. The intake air flow is adjusted to decrease and then remainapproximately constant, the exhaust flow is adjusted to remainapproximately constant, and the coolant flow is adjusted to decrease andthen remain approximately constant.

In this way, the controller within the engine system may regulate theflow of gases to the heat exchanger from the intake system and/or theexhaust system based on engine operating conditions. The controller mayalso regulate the flow of gases from the heat exchanger to one or morelocations within the intake system and one or more locations within theexhaust system based on engine operating conditions. The flow of gasesand/or coolant to/from the heat exchanger may be influenced at least inpart by the temperature of the output of the energy recovery device, andone of either the measured temperature of exhaust gas within the exhaustsystem or the estimated temperature of exhaust gas within the heatexchanger. The controller may compared the energy recovery device outputto the threshold output to adjust flows of intake air, exhaust gas,and/or coolant through the heat exchanger based on the estimated exhausttemperature or the measured exhaust temperature. The technical effect ofadjusting intake air flow, exhaust gas flow, and/or coolant flow to theheat exchanger in response to energy recovery device output is tocontrol the temperature of the gases discharged from the heat exchangerto the intake/exhaust system, and to generate electrical energyefficiently using the energy recovery device. In one example, the flowof gases and/or coolant to the heat exchanger may be adjusted in orderto increase the conversion of thermal energy of exhaust gas intoelectrical energy by the energy recovery device. In another example, theoutput of the energy recovery device may be adjusted in order toincrease or decrease the estimated temperature of exhaust gas within theheat exchanger. In this way, the temperature of the gases can becontrolled and provided for SAI, LP EGR, HP EGR, and compressor surgereduction to increase engine efficiency. Additionally, exhaust gasthermal energy can be utilized as electrical energy via the energyrecovery device of the heat exchanger, and engine performance may beincreased.

In one embodiment, a method for a gas mixing tank reservoir includesadjusting a flow of coolant through a gas mixing tank reservoir fluidlycoupled to each of an intake system and exhaust system of an engine inresponse to a request to supply one or more of secondary air injectionto the exhaust system and exhaust gas recirculation to the intake systemvia the reservoir, based on a temperature of the coolant entering thereservoir. In a first example of the method, the method includes afteradjusting the flow of coolant through the reservoir, supplying the oneor more of secondary air injection and exhaust gas recirculation asrequested in response to a temperature of gases within the reservoirbeing at a desired temperature, where the desired temperature is basedon an indicated location for injecting the gases from the reservoir toone or more of the intake system and exhaust system. A second example ofthe method optionally includes the first example and further includeswhen the request is a request to supply secondary air injection to theexhaust system, selectively supplying secondary air injection to anexhaust manifold and turbine bypass disposed around a turbine based on afirst temperature of a pre-turbine catalyst and second temperature of apost-turbine catalyst. A third example of the method optionally includesone or more or both of the first and second examples, and furtherincludes wherein selectively supplying secondary sir injection includessupplying secondary air injection to the exhaust manifold in response tothe first temperature being below a first catalyst light off temperatureof the pre-turbine catalyst and supplying secondary air injection to theturbine bypass in response to the second temperature being below asecond catalyst light off temperature of the post-turbine catalyst. Afourth example of the method optionally includes one or more or each ofthe first through third examples, and further includes wherein, inresponse to the request being a request to supply secondary airinjection to the exhaust system, adjusting the flow of coolant includes:increasing the flow of coolant through the reservoir when the coolanttemperature is greater than a threshold temperature; and decreasing theflow of coolant through the reservoir when the coolant temperature isless than the threshold temperature. A fifth example of the methodoptionally includes one or more or each of the first through fourthexamples, and further includes after adjusting the flow of coolantthrough the reservoir, delaying supplying the secondary air injection tothe exhaust system until the coolant temperature reaches a desiredcoolant temperature for secondary air injection. A sixth example of themethod optionally includes one or more or each of the first throughfifth examples, and further includes wherein the threshold temperatureis adjusted based on a gas temperature within the reservoir before theadjusting and the desired coolant temperature for secondary airinjection. A seventh example of the method optionally includes one ormore or each of the first through sixth examples, and further includeswherein adjusting the flow of coolant includes maintaining a currentflow of coolant through the reservoir in response to the request being arequest to supply secondary air injection to the exhaust system in orderto increase turbine speed only, regardless of the temperature of thecoolant entering the reservoir. An eighth example of the methodoptionally includes one or more or each of the first through seventhexamples, and further includes wherein, in response to the request beinga request to supply low pressure exhaust gas recirculation to the intakesystem, upstream of a compressor, adjusting the flow of coolantincludes: increasing the flow of coolant through the reservoir when thecoolant temperature is greater than a threshold temperature andcondensate is indicated at the compressor or when the coolanttemperature is less than the threshold temperature and condensate is notindicated at the compressor; and decreasing the flow of coolant throughthe reservoir when the coolant temperature is greater than the thresholdtemperature and condensate is not indicated at the compressor or whenthe coolant temperature is less than the threshold temperature andcondensate is indicated at the compressor. A ninth example of the methodoptionally includes one or more or each of the first through eighthexamples, and further includes wherein, in response to the request beinga request to supply high pressure exhaust gas recirculation to theintake system, downstream of a compressor, adjusting the flow of coolantincludes: increasing the flow of coolant through the reservoir when thecoolant temperature is less than a threshold temperature; and decreasingthe flow of coolant through the reservoir when the coolant temperatureis greater than the threshold temperature. A tenth example of the methodoptionally includes one or more or each of the first through ninthexamples, and further includes adjusting the flow of coolant through thereservoir in response to a request to supply air injection to the intakesystem, upstream of a compressor, based on compressor surge, whereinadjusting the flow of coolant includes: increasing the flow of coolantthrough the reservoir when the coolant temperature is greater than athreshold temperature; and decreasing the flow of coolant through thereservoir when the coolant temperature is less than the thresholdtemperature. An eleventh example of the method optionally includes oneor more or each of the first through tenth examples, and furtherincludes storing gases from one or more of the intake system and exhaustsystem in response to one or more of an amount of charge stored withinthe gas mixing tank reservoir being below a threshold level, boostpressure greater than a desired boost pressure for torque demand, and adeceleration fuel shut off condition.

In another embodiment, a method for a gas mixing tank reservoir includesduring a first condition, circulating coolant to a gas mixing tankreservoir arranged between and intake system and exhaust system of anengine and providing one or more of secondary air injection to theexhaust system and exhaust gas recirculation to the intake system viathe gas mixing tank reservoir; and during a second condition, notcirculating coolant to the gas mixing tank reservoir and providing oneor more of secondary air injection to the exhaust system and exhaust gasrecirculation to the intake system via the gas mixing tank reservoir. Ina first example of the method, the method includes wherein the firstcondition includes in response to one or more of: a request to providesecondary air injection to the exhaust system when a temperature ofcoolant entering the gas mixing tank reservoir is greater than a firstthreshold temperature; a request to provide low pressure exhaust gasrecirculation to the intake system, upstream of a compressor, when thetemperature of the coolant is greater than a second thresholdtemperature and condensate is indicated at the compressor; a request toprovide low pressure exhaust gas recirculation to the intake system,upstream of the compressor, when the temperature of the coolant is at orless than the second threshold temperature and condensate is notindicated at the compressor; and a request to provide high pressureexhaust gas recirculation to the intake system, downstream of thecompressor, when the temperature of the coolant is at or less than athird threshold temperature. A second example of the method optionallyincludes the first example and further includes wherein the secondcondition includes in response to one or more of: a request to providesecondary air injection to the exhaust system when a temperature ofcoolant entering the gas mixing tank reservoir is at or less than afirst threshold temperature; a request to provide low pressure exhaustgas recirculation to the intake system, upstream of a compressor, whenthe temperature of the coolant is greater than a second thresholdtemperature and condensate is not indicated at the compressor; a requestto provide low pressure exhaust gas recirculation to the intake system,upstream of the compressor, when the temperature of the coolant is at orless than the second threshold temperature and condensate is indicatedat the compressor; and a request to provide high pressure exhaust gasrecirculation to the intake system, downstream of the compressor, whenthe temperature of the coolant is greater than a third thresholdtemperature. A third example of the method optionally includes one ormore or both of the first and second examples, and further includesduring the first condition and second condition, delaying providing oneor more of the secondary air injection and exhaust gas recirculation viathe gas mixing tank reservoir until a gas temperature within the gasmixing tank reservoir reaches a desired temperature, where the desiredtemperature is based on a requested location in the intake system orexhaust system for injecting gases from the gas mixing temperaturereservoir.

In one embodiment, a system for an engine includes a gas mixing tankreservoir positioned between an intake system and exhaust system of theengine including: a first gas inlet port fluidly coupled to an exhaustmanifold; a second gas inlet port fluidly coupled to an intake passagedownstream of a compressor; a first gas outlet port fluidly coupled tothe intake passage; a second gas outlet port fluidly coupled to theexhaust system; coolant passages configured to flow coolant through thereservoir; and a first valve fluidly coupled to the coolant passages andconfigured to adjust the flow of coolant through the coolant passages.In a first example of the system for an engine, the system for an engineincludes a controller including computer readable instructions foradjusting a position of the first valve in response to a request tosupply one or more of gas stored within the reservoir to the exhaustsystem via the second gas outlet port and gas stored within thereservoir to the intake system via the first gas outlet port, based on atemperature of the coolant entering the coolant passages. A secondexample of the system for an engine optionally includes the firstexample and further includes wherein the second gas outlet port isselectively coupled via a second valve to each of the exhaust manifoldand turbine bypass passage disposed around a turbine of the exhaustsystem. A third example of the system for an engine optionally includesone or more or both of the first and second examples, and furtherincludes wherein the first gas outlet port is fluidly coupled to theintake passage upstream of the compressor and wherein the gas mixingtank reservoir further comprises a third gas outlet port fluidly coupledto the intake passage downstream of the compressor.

In one embodiment, a method for a heat exchanger includes flowing intakeair through the heat exchanger and selectively to each of an intakesystem and an exhaust system; flowing exhaust gas through an energyrecovery device coupled with the heat exchanger, through the heatexchanger, and selectively to each of the intake and exhaust system; andadjusting the flow of intake air and exhaust gas through the heatexchanger in response to an output of the energy recovery device. In afirst example of the method, the method includes wherein flowing exhaustgas includes flowing exhaust gas directly from the energy recoverydevice to the heat exchanger and wherein the flow of intake air andexhaust gas do not mix within the heat exchanger. A second example ofthe method optionally includes the first example and further includesduring flowing intake air and exhaust through the heat exchanger,transferring thermal energy between the intake air and exhaust gaswithin the heat exchanger. A third example of the method optionallyincludes one or more or both of the first and second examples, andfurther includes adjusting a flow of coolant through the heat exchangerin response to the output of the energy recovery device. A fourthexample of the method optionally includes one or more or each of thefirst through third examples, and further includes wherein adjusting theflow of coolant includes decreasing the flow of coolant through the heatexchanger as the output of the energy recovery device increases. A fifthexample of the method optionally includes one or more or each of thefirst through fourth examples, and further includes wherein adjustingthe flow of intake air and exhaust gas through the heat exchangerincludes one or more of decreasing the flow of intake air through theheat exchanger as the output of the energy recovery device increases, ordecreasing the flow of exhaust gas through the heat exchanger as theoutput of the energy recovery device increases toward a threshold energyoutput. A sixth example of the method optionally includes one or more oreach of the first through fifth examples, and further includesestimating a temperature of exhaust gas entering the heat exchanger fromthe energy recovery device based on the output of the energy recoverydevice and one or more of a temperature of the exhaust gas in theexhaust system and engine load. A seventh example of the methodoptionally includes one or more or each of the first through sixthexamples, and further includes operating the energy recovery device inresponse to one or more of an engine torque output increasing above athreshold engine torque output, and an exhaust gas temperature withinthe exhaust system increasing above a threshold exhaust gas temperature.An eighth example of the method optionally includes one or more or eachof the first through seventh examples, and further includes notoperating the energy recovery device in response to one or more of anengine torque output decreasing below a threshold engine torque output,an exhaust gas temperature within the exhaust system decreasing below athreshold exhaust gas temperature, an active particulate filterregeneration, and an engine cold start, and flowing exhaust gas throughthe energy recovery device, without transferring heat from the exhaustgas, and to the heat exchanger. A ninth example of the method optionallyincludes one or more or each of the first through eighth examples, andfurther includes wherein flowing intake air through the heat exchangerand selectively to each of the intake system and the exhaust systemincludes adjusting a first valve to adjust the flow of intake air fromthe heat exchanger to the intake system, upstream of a compressor, andadjusting a second valve to adjust the flow of intake air from the heatexchanger to each of a location in the exhaust system upstream of afirst catalyst and a location in the exhaust system downstream of thefirst catalyst. A tenth example of the method optionally includes one ormore or each of the first through ninth examples, and further includeswherein flowing exhaust gas through the heat exchanger and selectivelyto each of the intake and exhaust system includes adjusting a singlevalve to adjust the flow of exhaust gas to each of the intake systemupstream of a compressor, the intake system downstream of thecompressor, and the exhaust system upstream of a turbine.

In one embodiment, a system includes: a heat exchanger coupled to eachof an intake system and exhaust system and including a first set ofpassages configured to flow intake air from the intake system and to oneor more of the intake and exhaust system and a second set of passagesconfigured to flow exhaust gases from the exhaust system and to one ofthe intake system and exhaust system; and an energy recovery deviceintegrated with the heat exchanger and fluidly coupled to each of theexhaust system and the second set of passages, where exhaust gases flowfrom the exhaust system, through the energy recovery device, and intothe second set of passages. In a first example of the system, the systemincludes an outlet port of the energy recovery device directly coupledto an exhaust passage within the heat exchanger. A second example of thesystem optionally includes the first example and further includeswherein the heat exchanger includes: a first inlet port coupled to eachof the intake system, via a first valve, and the first set of passages;a second inlet port directly coupled to the energy recovery device andthe second set of passages; a first outlet port coupled to the first setof passages and selectively coupled to each of the intake system,upstream of a compressor via a second valve and the exhaust system via athird valve; and a second outlet port coupled to the second set ofpassages and selectively coupled to each of the intake system upstreamof the compressor, the intake system downstream of the compressor, andthe exhaust system via a fourth valve. A third example of the systemoptionally includes one or more or both of the first and secondexamples, and further includes wherein the energy recovering device isselectively fluidly coupled to each of the exhaust system upstream of afirst exhaust catalyst and a turbine and the exhaust system downstreamof the turbine via a fifth valve. A fourth example of the systemoptionally includes one or more or each of the first through thirdexamples, and further includes a controller including memory withnon-transitory computer-readable instructions for adjusting one or moreof the first, second, third, fourth, and fifth valves based on an outputof the energy recovery device. A fifth example of the system optionallyincludes one or more or each of the first through fourth examples, andfurther includes wherein the heat exchanger further includes a third setof passages configured to flow coolant, where the third set of passagesare positioned between each of the first set of passages and second setof passages. A sixth example of the system optionally includes one ormore or each of the first through fifth examples, and further includeswherein the energy recovery device includes a thermoelectric generatoradapted to convert thermal energy from exhaust gases to electricalenergy and output the electrical energy to a battery electricallycoupled to the energy recovery device.

In another embodiment of a system, the system includes: a heat exchangerincluding a first set of passages configured to flow intake air from anintake system and selectively to each of the intake system and anexhaust system, a second set of passages configured to flow exhaust gasfrom an exhaust system and selectively to each of the intake systemupstream of a compressor, the intake system downstream of a compressor,and the exhaust system, and a third set of passages configured tocirculate coolant; an energy recovery device physically and fluidlycoupled with the heat exchanger and including a fourth set of passagesdirectly coupled between the exhaust system and the second set ofpassages; and a controller including non-transitory memory with computerreadable instructions for: adjusting a flow of one or more of intake airthorough the first set of passages, exhaust gas through the second setof passages, and coolant through the third set of passages based on anamount of energy generated by the energy recovery device. In a firstexample of the system, the system includes an electrical componentelectrically coupled to a battery electrically coupled to and receivingelectrical energy from the energy recovery device and wherein thecomputer readable instructions further include instructions foroperating the electrical component using energy stored at the batteryvia the energy recovery device.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method, comprising: flowing intake airthrough a heat exchanger and selectively to each of an intake system andan exhaust system; flowing exhaust gas through an energy recovery devicecoupled with the heat exchanger, through the heat exchanger, andselectively to each of the intake and exhaust systems; and adjusting aflow of coolant through the heat exchanger based on a temperature ofcoolant entering the heat exchanger.
 2. The method of claim 1, whereinflowing exhaust gas includes flowing exhaust gas directly from theenergy recovery device to the heat exchanger and wherein the flow ofintake air and exhaust gas do not mix within the heat exchanger.
 3. Themethod of claim 1, further comprising adjusting the flow of intake airand exhaust gas through the heat exchanger in response to an output ofthe energy recovery device.
 4. The method of claim 3, further comprisingfurther adjusting the flow of coolant through the heat exchanger inresponse to the output of the energy recovery device, where adjustingthe flow of coolant includes decreasing the flow of coolant through theheat exchanger as the output of the energy recovery device increases. 5.The method of claim 3, wherein adjusting the flow of intake air andexhaust gas through the heat exchanger includes one or more ofdecreasing the flow of intake air through the heat exchanger as theoutput of the energy recovery device increases, or decreasing the flowof exhaust gas through the heat exchanger as the output of the energyrecovery device increases toward a threshold energy output.
 6. Themethod of claim 1, further comprising, in response to a request tosupply intake air for secondary air injection to the exhaust system,selectively flowing intake air from the heat exchanger to an exhaustmanifold and a turbine bypass disposed around a turbine based on a firsttemperature of a pre-turbine catalyst and a second temperature of apost-turbine catalyst.
 7. The method of claim 1, further comprising, inresponse to a request to supply intake air for secondary air injectionto the exhaust system: increasing the flow of coolant through the heatexchanger when the coolant temperature is greater than a thresholdtemperature; and decreasing the flow of coolant through the heatexchanger when the coolant temperature is less than the thresholdtemperature.
 8. The method of claim 7, further comprising, afteradjusting the flow of coolant through the heat exchanger, delayingsupplying the intake air for secondary air injection to the exhaustsystem until the coolant temperature reaches a desired coolanttemperature for secondary air injection and wherein the thresholdtemperature is adjusted based on a gas temperature within the heatexchanger before the adjusting and the desired coolant temperature forsecondary air injection.
 9. The method of claim 1, further comprising,in response to a request to supply low pressure exhaust gasrecirculation to the intake system, upstream of a compressor, adjustingthe flow of coolant includes: increasing the flow of coolant through theheat exchanger when the coolant temperature is greater than a thresholdtemperature and condensate is indicated at the compressor or when thecoolant temperature is less than the threshold temperature andcondensate is not indicated at the compressor; and decreasing the flowof coolant through the heat exchanger when the coolant temperature isgreater than the threshold temperature and condensate is not indicatedat the compressor or when the coolant temperature is less than thethreshold temperature and condensate is indicated at the compressor. 10.The method of claim 1, further comprising, in response to a request tosupply high pressure exhaust gas recirculation to the intake system,downstream of a compressor, adjusting the flow of coolant includes:increasing the flow of coolant through the heat exchanger when thecoolant temperature is less than a threshold temperature; and decreasingthe flow of coolant through the heat exchanger when the coolanttemperature is greater than the threshold temperature.
 11. The method ofclaim 1, further comprising operating the energy recovery device inresponse to one or more of an engine torque output increasing above athreshold engine torque output, and an exhaust gas temperature withinthe exhaust system increasing above a threshold exhaust gas temperature.12. The method of claim 1, further comprising not operating the energyrecovery device in response to one or more of an engine torque outputdecreasing below a threshold engine torque output, an exhaust gastemperature within the exhaust system decreasing below a thresholdexhaust gas temperature, an active particulate filter regeneration, andan engine cold start, and flowing exhaust gas through the energyrecovery device, without transferring heat from the exhaust gas, to theheat exchanger.
 13. A method, comprising: flowing coolant through a setof coolant passages of a heat exchanger fluidly coupled to each of anintake system and an exhaust system of an engine and adjusting the flowof coolant in response to a request to supply one or more of secondaryair injection to the exhaust system and exhaust gas recirculation to theintake system via the heat exchanger, based on a temperature of thecoolant entering the heat exchanger; flowing intake air through a set ofair passages of the heat exchanger and selectively to one or more of theintake system and the exhaust system; and flowing exhaust gas through aset of exhaust passages of the heat exchanger and selectively to one ormore of the intake system and the exhaust system.
 14. The method ofclaim 13, wherein flowing exhaust gas includes first flowing exhaust gasfrom the exhaust system through an energy recovery device coupled withthe heat exchanger and then flowing exhaust gas directly from the energyrecovery device to the set of exhaust passages.
 15. The method of claim14, further comprising operating the energy recovery device in responseto one or more of an engine torque output increasing above a thresholdengine torque output, and an exhaust gas temperature within the exhaustsystem increasing above a threshold exhaust gas temperature.
 16. Themethod of claim 13, wherein adjusting the flow of coolant includes: inresponse to a request to supply intake air for secondary air injectionto the exhaust system, increasing the flow of coolant through the heatexchanger when the coolant temperature is greater than a first thresholdtemperature and decreasing the flow of coolant through the heatexchanger when the coolant temperature is less than the first thresholdtemperature; in response to a request to supply low pressure exhaust gasrecirculation (EGR) to the intake system, upstream of a compressor,increasing the flow of coolant through the heat exchanger when thecoolant temperature is greater than a second threshold temperature andcondensate is indicated at the compressor or when the coolanttemperature is less than the second threshold temperature and condensateis not indicated at the compressor and decreasing the flow of coolantthrough the heat exchanger when the coolant temperature is greater thanthe second threshold temperature and condensate is not indicated at thecompressor or when the coolant temperature is less than the secondthreshold temperature and condensate is indicated at the compressor; andin response to a request to supply high pressure EGR to the intakesystem, downstream of the compressor, increasing the flow of coolantthrough the heat exchanger when the coolant temperature is less than athird threshold temperature and decreasing the flow of coolant throughthe heat exchanger when the coolant temperature is greater than thethird threshold temperature.
 17. A system for an engine, comprising: aheat exchanger positioned between an intake system and an exhaust systemof the engine including: a first gas inlet port fluidly coupled to anexhaust manifold; a second gas inlet port fluidly coupled to an intakepassage downstream of a compressor; a first gas outlet port fluidlycoupled to the intake passage; a second gas outlet port fluidly coupledto the exhaust system; coolant passages configured to flow coolantthrough the heat exchanger, the coolant passages coupled between acoolant inlet port of the heat exchanger and a coolant outlet port ofthe heat exchanger; and a first valve fluidly coupled to the coolantpassages and configured to adjust the flow of coolant through thecoolant passages.
 18. The system of claim 17, further comprising anenergy recovery device integrated with the heat exchanger and fluidlycoupled to each of the first gas inlet port and a set of passages of theheat exchanger configured to flow exhaust gases.
 19. The system of claim17, further comprising a controller including computer readableinstructions for adjusting a position of the first valve in response toa request to supply one or more of gas stored within the heat exchangerto the exhaust system via the second gas outlet port and gas storedwithin the heat exchanger to the intake system via the first gas outletport, based on a temperature of the coolant entering the coolantpassages.
 20. The system of claim 17, wherein the first gas outlet portis fluidly coupled to the intake passage upstream of the compressor andwherein the heat exchanger further comprises a third gas outlet portfluidly coupled to the intake passage downstream of the compressor.